Optimal foraging theory predicts that predators should include less prey categories in their diet (become specialists)…
a. where competitor density is high
b. where the environment is unproductive.
c. if prey handling times are long compared to search times.
d. if prey handling times are short compared to search times.

The correct option is : c. if prey handling times are long compared to search times.

Explanation:

The optimal foraging theory is a model that predicts the behavior of an animal, while searching for food. According to this theory, the diet of an animal predicts the forging strategy used by the animal. The forging strategy adopted by an animal involves maximizing the gained energy.  

According to the optimal foraging theory, predators with narrow diets have longer prey handling times as compared to search times. Such predators are known to have a specialist strategy of forging.

i think the answer is

mass

a. the production of carbon dioxide through the process of photosynthesis