Q: In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").
A herd of wild horses has been decreasing in size rapidly. Which of these might be the cause? (A) There has been a lot of rain (B) The month of July has arrived (C) Predators have moved out of the area (D) All of the vegetation has been dying
A:
D