Final answer:
Cells containing salivary amylase function best at a pH close to 6.9 and are less effective under too acidic or too alkaline conditions.
Step-by-step explanation:
From the information given, it can be inferred that cells that have salivary amylase do not function well at a pH that is too high or too low. Salivary amylase has an optimum pH of 6.9 and is inactivated by the acidic pH of the stomach where hydrochloric acid (HCl) is present. This indicates that salivary amylase is adapted to work best at a specific pH range and would not maintain its activity at significantly different pH levels.