There are a lot of computers in the lab and they need professional to make sure they can

问题补充：

There are a lot of computers in the lab,and they need professional to make sure they can be in a good state.

A. operation

B. maintenance

C. service

D. advice

答案：

A. operation

(答案→)B. maintenance

C. service

D. advice

解析：operation操作；maintenance 维护,保持；service服务；advice建议。这里指计算机的专业维护。