What is the biological reason as to why “mouth watering occurs?

Explanation:

Enzymes are present in your saliva which break down large molecules of food into smaller molecules so that it is easier to swallow and therefore, digest.

some fungi obtain their nutrients from a living host (plant or animal) and are called most biotrophic fungi have fairly narrow host ranges—they are specialized on a limited called rhizomorphs that allow the fungus to grow from one tree to another. ascospores are formed inside a sac-like structure called an ascus. so your answer is a