Isabella and Mariagirls.A. are allB. are bothC. all areD. is both

问题补充：

Isabella and Mariagirls.

A. are all

B. are both

C. all are

D. is both

答案：

A. are all

(答案→)B. are both

C. all are

D. is both

解析：句意:Isabella和Maria都是女孩。both 表示两者都；all 表示三者或以上都。根据句意可以排除A和C。both 应该放在be 动词的后面，实义动词的前面。故应选B。