Biotechnology is the use of living systems and organisms to develop or make products, or "any technological application that uses biological systems, living organisms or derivatives thereof, to make or modify products or processes for specific use. For thousands of years, humankind has used biotechnology in agriculture, food production, and medicine. 

Application of biotechnology occurs in agriculture, biomedicine and environmental field.

Biotechnology is the use of biological processes, organisms, or systems to manufacture products intended to improve the quality of human life. The earliest biotechnologists were farmers who developed improved species of plants and animals by cross pollination or cross breeding. 

Citric acid is a weak organic acid with the formula -CHO. It is a natural preservative or conservative which occurs naturally in citrus fruits and is also used to add an acidic or sour taste to foods and drinks. Griseofulvin is an orally administered antifungal drug. It is used both in animals and humans, to treat fungal infections of the skin and nails. Whereas cephalosporins are a group of broad spectrum, semi-synthetic beta-lactam antibiotics derived from the mould Cephalosporium. Streptomycin is an antibiotic (antimycobacterial) drug, the first of a class of drugs called as aminoglycosides to be discovered,

The correct option is C

Modern biotechnology is based on the the methods of genetic engineering.  It is a technique which involves the introduction of foreign DNA carrying the desired gene of interest into the host organism & thus change the phenotype of the host organism.

Genetic engineering aims to add new DNA to an organism to add one or more new favorable traits that are not found in that organism. Genes are the DNA segments that carry the genetic information for the production of particular proteins/ enzymes. These enzymes/proteins determine the traits of an organism, thus alteration in gene structure is the key to impart new traits to the organisms. The genetic information present in genes is copied to the RNA and finally into the proteins; further genes are inherited from generation to generation. Hence, manipulation of RNA, protein or extranuclear gene will be confined to that generation only. Hence, genetic engineering is the manipulation of genes.

Briggs and King discovered that normal hatched tadpoles can be obtained by transplanting the nucleus of a blastula cell to the enucleated eggs of Rana pipiens. This finding provided an initial answer to the long-standing question of whether the process of development and cell differentiation requires a loss or stable change in the genetic constitution of cells.

Har Govind Khorana synthesized artificial gene in a test tube in the year 1969.

• Hirudin is a potent inhibitor of thrombin. Thus, it has a high therapeutic value in the treatment of thrombosis.
  
• Hirudin gene inserted in Brassica napus was synthesized chemically in E. coli and yeast and was found to be a reasonable success. Extended work suggested the production of this protein in a plant system, particularly oil-producing crop.
  

The therapeutic techniques used to treat deleterious phenotypic effects of a genetic defect especially without altering the genetic makeup of the germplasm of the individual is known as Euphenics. Therefore it is the improvement of phenotypic effect in humans after their birth by genetic engineering. Hence option B is correct.

Transgenic mice are being formed for use in testing the safety of before they are used they are used on human beings. They are being used to test the safety of the polio vaccine. The first transgenic cow. Rosie produced human protein enriched milk (2.4 gms per litre). The milk contained the human alphalactalbumin. It is a more balanced product for human babies than natural cow-milk. Bulls with more power are produced by animal breeding not by genetic engineering. So, the correct answer is 'Transgenic mice for testing safety of polio vaccine before use in humans'.

A xenobiotic is a foreign chemical substance found within an organism that is not normally naturally produced by or expected to be present within that organism. The term xenobiotics is often used in the context of pollutants such as dioxins and polychlorinated biphenyls and their effect on the biota, because xenobiotics are understood as substances foreign to an entire biological system, i.e., artificial substances, which did not exist in nature before their synthesis by humans. 

Klebsiella pneumoniae is a Gram-negative, non-motile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium. It naturally occurs in the soil, and about 30% of strains can fix nitrogen in anaerobic conditions.

The basic process of recombinant DNA technology revolves around the activity of DNA in the synthesis of protein. By intervening in this process, scientists can change the nature of the DNA and of the gene make-up of an organism. By inserting genes into the genome of an organism, the scientist can induce the organism to produce a protein it does not normally produce. The genes used in DNA technology are commonly obtained from host cells or organisms called as gene libraries. A gene library is a collection of cells identified as harbouring a specific gene. For example, E. coli cells can be stored with the genes for human insulin in their chromosomes. Vaccines represent another application of recombinant DNA technology. For instance, the hepatitis B vaccine now in use is composed of viral protein manufactured by yeast cells, which have been recombined with viral genes. 

Genetic engineering, also called as genetic modification, is the direct manipulation of an organism's genome using biotechnology. New DNA is inserted in the host genome by first isolating and copying the genetic material of interest using molecular cloning methods to generate a DNA sequence, or by synthesizing the DNA and then inserting this construct into the host organism. Genetic engineering techniques have been applied in numerous fields including research, agriculture, industrial biotechnology, and medicine. Enzymes used in laundry detergent and medicines such as insulin and human growth hormone are now manufactured in GM cells, experimental GM cell lines and GM animals such as mice or zebrafish are being used for research purposes, and genetically modified crops have been commercialized.

In 1973 Herbert Boyer, of the University of California at San Francisco, and Stanley Cohen, at Stanford University, reported the construction of functional organisms that combined and replicated genetic information from different species. Their experiments dramatically demonstrated the potential impact of DNA recombinant engineering on medicine and pharmacology, industry and agriculture.

Bacteria were the first organisms to be genetically modified. Plasmid DNA containing new genes can be inserted into the bacterial cell and the bacteria will then express those genes. These genes can code for medicines or enzymes that process food and other substrates.

Tissue plasminogen activator is a clot-dissolving enzyme that is produced naturally by cells in the walls of blood vessels and catalyzes the conversion of plasminogen to plasmin. A preparation of this enzyme is produced by genetic engineering and used to dissolve clots blocking coronary arteries in heart attack and cranial arteries in certain cases of stroke.

Genetic engineering is possible because all organisms are based on the same genetic code. DNases which act on specific positions or sequences on the DNA are called as restriction endonucleases. The sequences which are recognised by the restriction endonucleases or restriction enzymes (RE) are called as recognition sequences restriction sites. These sequences are palindromic sequences. Different restriction enzymes present in different bacteria can recognize different or same restriction sites but they will cut at two different points within the restriction site. No two restriction enzymes from a single bacterium will cut at the same restriction site. 

Genetic engineering is the process of replicating a specific set of genes from a strand of DNA. It is the process of using gene cloning and other genetic manipulation tools to achieve isolate specific genes.