The correct answer is Carbohydrates.

Important Points

• The human digestive system consists of two parts, alimentary canal, and associated glands.
• The mouth leads food to be digested into buccal cavity.
• The digestion of carbohydrates begins in buccal cavity.
• The buccal cavity performs two major functions
  • Mastication of food.
  • Facilitation of swallowing. A digestive enzyme, salivary amylase, in saliva begins digestion of 

carbohydrates

• The chemical process of digestion is initiated in oral cavity by hydrolytic action of salivary amylase.
• From mouth, food reaches stomach through a food pipe called oesophagus.
• There is no digestion inside food pipe.

Additional Information 

• The digestion of fat begins in stomach.
  • Lipase is digestive enzyme of fat.
• The digestion of protein occurs in stomach and duodenum.
  • Pepsin is digestive enzyme of protein.

The correct answer is amino acids.

Key Points

• When protein reaches our stomach, hydrochloric acid and enzymes called proteases (also called a peptidase or proteinase) break it down into smaller chains of amino acids. 
• From our stomach, se smaller chains of amino acids move into small intestine.
• As this happens, pancreas releases enzymes and a bicarbonate buffer that reduces acidity of digested food.
• This reduction allows more enzymes to work on furr breaking down amino acid chains into individual amino acids.

Additional Information

• Carbohydrates - It is digested by amylase, converted into glucose, and is finally converted into glycogen for storage. 
• Starch - It is a special type of carbohydrate and is digested in a similar manner. 
• Small globules - It is basically a small drop or ball of a liquid floating in a medium. 
• A protease (also called a peptidase or proteinase) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring formation of new protein products.