问题
选择题
If human beings had been a bit less greedy and cruel, more birds and animals _____dying out.
A．ought to avoid
B．could have been avoided
C．should have avoided
D．might have avoided
答案
答案：D
本题涉及虚拟语气的使用，从if引导的从句分析可以知道与过去相反，should have done表示本来不应该但实际上干了，不符合题意。