确定器官移植受体的首要标准是：（）
A.受体在家庭中的地位
B.受体过去的成就
C.受体未来的贡献
D.移植的禁忌症与适应症
参考答案：D
— Did you visit the museum today?
— No. We ______ it, but we spent too much time shopping.
A．could have visited
B．must have visited
C．may have visited
D．couldn’t have visited
核动力潜艇，可分为（）核潜艇和（）核潜艇。
