. Only in a few countries in the world _______ a reasonable standard of living.

A．enjoyed people have

B．people have enjoyed

C．people can enjoy

D．can people enjoy

劳动过程中的有害因素

A．太阳辐射
B．视觉紧张
C．炭疽杆菌
D．生产性毒物
E．噪声、振动