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

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

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

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

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