What part of the dead leaf cells are digested by the enzyme cellulase

The part of the dead leaf cells where the cellulase acts is in the cell wall.

Explanation:

Cellulase enzymes are used to break down the cellulose of plant cell walls into simple sugars that can be transformed (fermented) by microbes to fuels, primarily ethanol, as well as to chemicals, plastics, fibers, detergents, pharmaceuticals, and many other products.

The answer is the option c. fact. Indeed facts are the events such as they occur, without interpretations or opinions. Facts happens and they can be observed by different means: you can get them through sense organs (eye, ear, mouth, skin, nose) or with instruments. When you report facts you must clearly state them appart of your interpretation or opinion.