Option 1: This statement is incorrect. Fat present in the food is not digested by trypsin and chymotrypsin. Trypsin and chymotrypsin are proteolytic enzymes that digest proteins in the small intestine.

Option 2: This statement is incorrect. Lipases are enzymes that primarily digest fats, not starch. Starch is digested by amylase enzymes, which are present in saliva and the pancreas.

Option 3: This statement is correct. Fat of food is indeed digested by lipases. Lipases are enzymes that break down fats into smaller molecules called fatty acids and glycerol. These enzymes are primarily produced by the pancreas and are active in the small intestine.

Option 4: This statement is incorrect. Nucleic acids, which are found in foods like DNA and RNA, are not digested by amylases. They are digested by nucleases, which are enzymes that break down nucleic acids into smaller components like nucleotides.

In conclusion, the correct statement regarding digestion is Option 3: Fat of food is digested by lipases.