任何人不得在未进行氧气、可燃气体、有毒有害气体浓度检测的情况下从事（）作业。
参考答案：有限空间
You should do the things worth ____, and if you have difficulty _____ them, you can turn to your family.
A．doing; doing
B．doing; to do
C．being done; to do
D．being done; doing
MOTOROLA检验标准中规定检验员裸视视力最低要求：（）
A.1.0
B.1.1
C.1.5
D.1.2
