隔离开关加锁后，其中一把钥匙交车站值班员保管，存放在固定地点。（）
参考答案：对
—Have you heard from Nelly recently?
— Yes, I _________ his letters and cards many times while I was in Italy.
A．have received
B．received
C．had received
D．would receive
甲烷化炉床层有（）点温度达到（）℃，甲烷化联锁动作。
A.1380
B.2380
C.1430
D.1400
