Question

decrease in grass since they are most affected by pollutants.
gazelle numbers will decrease because they eat grass.
hawk numbers will decrease because they are a top predator.
foxes will decrease because they have fewer predators.

Explanation:

Biomagnification means pollutants accumulate and become more concentrated at higher trophic levels in a food chain. Top predators like hawks are at the highest level here, so they will accumulate the most pollutants, leading to a decrease in their numbers. The other options are incorrect: grass (producer) has the lowest pollutant concentration, gazelles (primary consumer) have less than top predators, and fewer predators would increase fox numbers, not decrease them.

Answer:

Hawk numbers will decrease because they are a top predator.