Introduction to Biology: Enzymes, enzyme function.
Enzymes are biomolecules that act as catalysts and accelerate chemical reactions. Most enzymes are proteins, and there are also some RNA molecules that act as enzymes.
All enzymes have an optimal temperature and pH at which the reaction has it maximun reaction rate, outside these parameters, the enzyme is less efficient and it can even loss it shape (denaturalization).
In this case, the optimal pH would be the one at which the time needed to produce 10 grames of maltose is the lowest. If we look at the table, the lowest times are 20 and 21 seconds, at a pH of 6 and 8 respectively, so the optimal pH is between 6 and 8.
This means the correct answer would be C. 7