National Forest Policy (1988) of India has recommended 33 percent forest cover for the plains and 67 percent for the hills.

If carnivores, which feed on deer are removed, then the deer population will flourish. Removal of 80% of tigers from an area will cause an increase in the population of herbivores, which would further feed on more vegetation thus, decreasing its growth. The length of the food chain is limited to 3−4 trophic levels as only 10% of energy is transferred to the next trophic level. Hence after 3−4 trophic levels, there is very little or no energy left to sustain more trophic levels.

Environment is the sum of all boo tic (living) and a biotin (non-living) factors that surround and practically influence the organism. All components are Inter-linked and inter-dependent. Biotin factors include different organism. Abiotic factors are non-living factors survival, form, function, behavior and reproduction of organism. There are many abiotic factors. The four major abiotic factors are temperature, water, light and soil. 

Forest is called as the green lung because they fix the carbon dioxide in the presence of sunlight and convert them into glucose by the process of photosynthesis. The reaction of carbon dioxide with water during this process releases oxygen as byproduct and glucose is formed. Thus forest replenishes oxygen in turn of carbon dioxide. Thus, the correct answer is option D.

• Forests are areas of biodiversity hot spots, as we know. They are full of plants, trees, animals and birds. 
• Even the dead bodies of plants and animals are decayed by saprophytes, supporting large forms of life. 
• In this process, they provide the soil with nutrients that help the seeds to grow properly and support new forms of life. So we can say that forests are dynamic living entities.

Crown of a tree is basically the aerial part of trees that contains branches, leaves and stems. Thus, it constitutes the branchy part of trees.

The animals living in the forests excrete the nitrogenous wastes which is acted upon by the microbes. The complex materials in the dung is converted into simpler form of nutrients. These nutrients are taken up by the plants and trees in the forests. The new seedling utilises the nutrients from this decayed dung. 

Forest is depleting day by day due to the rapid urbanisation. As urbanising is increasing rapidly thus forest is most rapidly depleting natural resource. 

• Turmeric has some antioxidant and anti-inflammatory properties and Basil is used for stomach spasms, loss of appetite, intestinal gas but they come under herbs, not a tree.
  
• Oak is mainly used for furniture purposes as Oak wood is exceedingly strong, heavy and durable.
  
• Neem tree has various medicinal properties such as antioxidant, anti-inflammatory, anti-diabetic, anticancer, antifungal, antiviral. 
• So, option A neem is the correct answer.
  

The taiga or northern temperate coniferous forest or boreal forests consist of evergreen, cone bearing trees.

Himalayan coniferous forests are altitudinal forests which occur in the Himalayas at the altitude of 1700-3000 m

The tropical dry deciduous forest biomes develop in the region where moisture relation are intermediate between desert and savanna. These are found in Southeast Asia, Central and South America, India and Northern Australia. Teak and Sal are major large tree.

The plants of the deciduous forests shed their leaves during one season. Its dominant climax vegetation consists of broad leaved hardwood (dicot) tree like Oak, Elm, Maple, Birch, etc.

• Forests cover 31 percent of the world's land surface i.e over 4 billion hectares. (One hectare = 2.47 acres.) .
• In India, the total forest and tree cover is spread across 802,088 square km, which is 24.39 percent of the geographical area of the country.
• Hence Land mass occupied by forest is about 11%.
• So, the correct answer is '11%'.

The percentage of land covered by forest in India is around 24.39%, which is approximately 802,088 square km

The forest floor is also called detritus and O horizon. It is one of the features of a forest ecosystem. It is known as the floor of the animal habitat. It consists of shed vegetative parts like leaves, branches, stems. It exists above the soil surface. Usually, insects that feed on the leaf litter are found on it. Examples of animals found on the forest floor include snake, lizards, butterflies.

In 1900, the forest cover of the world comprised about 7000 million hectors. In 2000, the forest cover of the world comprised only about 2370 million hector’s. It indicates that more than 50% of the tropical forests were converted into agricultural land.