Air resistance depends upon speed, so initially, when the body is increasing in speed, the acceleration will be decreasing. Hence A and C can be immediately discounted. Many candidates chose C which indicated that they clearly had not read the question carefully. As the body approaches terminal velocity so its acceleration approaches zero, indicating D as the correct answer. Unfortunately though, D also indicates a sudden decrease in the acceleration initially whereas it should be a gradual decrease (as in C). Both B and D were accepted as correct answers to this question.