on earth do you suppose this?A. What; could doB. What; could have doneC. Who; doD. Who; c

问题补充：

on earth do you suppose this?

A. What; could do

B. What; could have done

C. Who; do

D. Who; could have done

答案：

A. What; could do

B. What; could have done

C. Who; do

(答案→)D. Who; could have done

解析：句意：你究竟认为谁能做这件事？这里是特殊疑问句，do you suppose是插入语，插入语的语序必须是陈述语序，这里正好疑问词作主语，做事必须是某人来做所以排除AB，这里who做主语时，谓语动词应该用单数，故排除C。所以应选D。