Answer:
b
Step-by-step explanation:
The factor that is most likely to be responsible for the changes observed in the world's rainforest is human activities.
There has been a surge in the human population leading to an increased need for housing, foods, and other infrastructures. All these needs are directly or indirectly provided by the forest. Hence, the more the population of human expands, the more pressure that would be exerted on the rainforest and, indeed, other forests of the world.
The correct option is b.