The substances, which assist enzymes act, are called

Diastase
Substrates
Co-enzymes
None of the above

The correct answer is C. Co-enzymes.

Co-enzymes are non-protein molecules that are essential for the activity of enzymes. They are often derived from vitamins or minerals. Co-enzymes work by binding to the active site of an enzyme and helping to orient the substrate in the correct position for catalysis. They may also participate in the reaction itself, by donating or accepting electrons or groups.

Diastase is an enzyme that breaks down starch into sugars. It is found in saliva and pancreatic juice.

Substrates are the molecules that enzymes act on. They are the reactants in the enzymatic reaction.

None of the above is not the correct answer because it does not include all of the possible options.