The partially digested food coming from the stomach enters into a long and narrow tube P. Here, the liver secretes a liquid called Q which converts fats into tiny droplets. Pancreatic juice breaks down fats completely into R and glycerol. The intestinal juice breaks down the starch carbohydrate completely into T whereas proteins are broken down into U. 
Name the sac in which liquid Q is stored temporarily. 

The digested food in the small intestine is absorbed into blood vessels in the walls of the small intestine through millions of tiny finger-like outgrowths called W. The undigested and unabsorbed food from the small intestine enters into another organ X. The organ X absorbs most of the water from the undigested waste food material making it semi-solid. This semi-solid waste is stored in part Y of organ X for some time. It is passed out from the body through part Z in the form of faeces. What is W? (villi/mucus)

The digested food in the small intestine is absorbed into blood vessels in the walls of the small intestine through millions of tiny finger-like outgrowths called W. The undigested and unabsorbed food from the small intestine enters into another organ X. The organ X absorbs most of the water from the undigested waste food material making it semi-solid. This semi-solid waste is stored in part Y of organ X for some time. It is passed out from the body through part Z in the form of faeces. What is X?

If we do not clean our teeth and mouth after eating food, then many harmful microorganisms called 'A' begin to grow and live on the tooth. These microorganisms act on the substance 'B' present in the leftover food particles sticking to the tooth to form lactic acid. The lactic acid eats up the parts 'D' and dentine of the tooth gradually and ultimately makes a hole in the tooth. When this hole reaches part 'F' of the tooth, our tooth becomes painful, and we get a toothache. What is 'B'?

If we do not clean our teeth and mouth after eating food, then many harmful microorganisms called A begin to grow and live on the tooth. These microorganisms act on the substance B present in the leftover food particles sticking to the tooth to form C. The C eats up the parts D and E of the tooth gradually and ultimately make a hole in the tooth. When this hole reaches part F of the tooth, our tooth becomes painful and we get a toothache. What is C?