2. Give ONE possible reason, biotic or abiotic, why the population decreased in 1990 after it had reached its carrying capacity.

availability of resources.

Explanation:

Availability of resources is abiotic factor which is responsible for the decrease in population in 1990 because when the population reaches its carrying capacity so the organisms compete with each other and due to limited resources such as food etc the decrease occurs in population. Infection is also occurs when there is high population due to which death occurs and population of organism decreases.

i believe the correct answer is d

answer; i believe the answer is hydraulic action;