The correct option is A All of the above
The reason for the disappearance of smaller herbivores in Gorongosa national park was the unavailability of tender roots and leaves. The large herbivores eat away the bigger grass and trample them. This makes space for new tender grass to grow. Smaller herbivores feed on these tender grass. But when the larger animals were hunted down, there was no scope for new tender grass to grow. Slowly the small herbivores lost their source of food and started reducing in number. This proves that in a community all organisms are important. When one species gets affected, an imbalance is created and the repercussions are faced by other organisms as well.