10 years ago， _________ only one classroom building in our school. And in 10 years， _________ five classroom buildings in our school.

A．there will be, there are

B．there was, there will be

C．there will be; there was

D．there was, there are

当检查客户户内燃气管道时，发现有锈蚀的现象时，应如何处理。（）

A、经口头协议，立即进行维修

B、要给客户一份“户内隐患整改通知书”

C、无需经客户同意，维修人员可以进行维修