Only after reaching eighteen join the army.A. have you; you canB. have you; can you C. you

问题补充：

Only after reaching eighteen join the army.

A. have you; you can

B. have you; can you

C. you have; you can

D. you have; can you

答案：

A. have you; you can

B. have you; can you

C. you have; you can

(答案→)D. you have; can you

解析：only修饰状语，主句要倒装。