Question

1. plants would die in a pond after ______. *

a. the amount of oxygen decreased
b. humans were affected
c. larger animals went hungry
d. the amount of carbon dioxide decreased

Explanation:

Plants in a pond perform photosynthesis, which requires carbon dioxide ($CO_2$). If the amount of carbon dioxide decreases, plants can't photosynthesize properly, leading to their death. Option a: Oxygen decrease affects animals more directly. Option b: Human effect is indirect. Option c: Larger animals' hunger doesn't directly kill plants. So d is correct.

Answer:

d. the amount of carbon dioxide decreased