The correct answer is (c).

• Saliva is a thick, colourless and glistening liquid with about 98 per cent water in our mouth. The saliva contains chemicals like the mucus, salts, antibacterial substances and enzymes which help in the digestion of food especially starch.
• The digestion of starch into a sugar called the maltose is done because of an enzyme, salivary amylase that the saliva contains. 

Among other visceral organs larva contains well- developed paired glands called silk glands. Silk is the secretion of salivary gland.

• Saliva secreted by salivary glands doesn't give safety against dental caries.
  
• Dental carries take place due to deposition of food particles on teeth and subsequent bacterial decay.
  
• So, the correct option is 'Give safely against dental carries'.

• Plaque is a soft, sticky film that builds up on your teeth and contains millions of bacteria. 
• When you eat, the bacteria in plaque use the sugars in your food to produce acids that eat away at the tooth enamel. Hence, Sugar + Plaque → acids.

A dental disease characterised by mottling of teeth is due to the presence of an ingredient in drinking water, namely fluorine. Dental fluorosis or mottling of tooth enamel is a developmental disturbance of dental enamel caused by the consumption of excess fluoride during tooth development. The risk of fluoride overexposure occurs at any age but it is higher at younger ages.

Tooth decay is the softening of teeth enamels and refers to the damage of the structure of the tooth. This occurs due to high consumption of chocolates, sweets and cold drinks. Tooth decay is caused by acids that are created when plaque bacteria break down sugar in the mouth. 

Tooth decay starts with the erosion of tooth enamel and leads to holes in teeth called cavities. The measures to prevent tooth decay are to brush the teeth twice a day, dental floss, skip sugar, rising the mouth after meals.

In human, 3.pairs of salivary glands are present. They are sublingual , parotid  and submaxillary .

Chewing or mastication is the process by which food is crushed and ground my teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. So the correct option is 'Mastication of food '.

Pulp is the soft material in the tooth it is richly supplied with blood vessels and nerves.