The correct answer is option 4, amylase. Amylase is the first enzyme to mix with food in the digestive tract.

Let`s understand the other options to have a clearer picture. Option 1, trypsin, is an enzyme that acts on proteins and is produced in the pancreas. It plays a role in protein digestion, but it is not the first enzyme that mixes with food.

Option 2, cellulose, is a complex carbohydrate found in the cell walls of plants. It is a type of dietary fiber and cannot be digested by humans because we lack the enzyme cellulase needed to break it down. Therefore, cellulose does not mix with food in the digestive tract as an enzyme.

Option 3, pepsin, is an enzyme produced in the stomach and is involved in the digestion of proteins. It is secreted when food enters the stomach and begins the breakdown of proteins. However, pepsin is not the first enzyme to mix with food in the digestive tract.

Therefore, the correct answer is option 4, amylase. Amylase is an enzyme produced in the salivary glands and pancreas. It is released in the mouth during chewing and in the small intestine where it begins the