Mary opened the door. There she had never seen before.A. a boy did standB. did a boy stand

问题补充：

Mary opened the door. There she had never seen before.

A. a boy did stand

B. did a boy stand

C. a boy stood

D. stood a boy

答案：

A. a boy did stand

B. did a boy stand

C. a boy stood

(答案→)D. stood a boy

解析：可联系答.案.网客服索取。