— _____!
— It's OK. [ ]
A. I'm sorry
B. Hi
C. Watch out
答案:A
Everyone should do something ______ wild animals.
A.to protect
B.protecting
C.protect
D.to protecting
凡经常检修的部位应设可靠的隔断装置,下列设备()为可靠的隔断装置。
A.插板阀
B.闸阀
C.蝶阀
D.水封