企业质量体系主要满足()的要求。
A.所有各类合同
B.认证
C.顾客
D.认证与顾客
参考答案：D
By the time she ________ tomorrow, the work ________.
A．arrives ; will be finished
B．arrives ; will have been finished
C．will arrive ; will have been finished
D．arrives ; will have finished
Scientists are convinced______ the positive effect of laughter______ physical and mental health.
A．of ; at
B．by ; in
C．of ; on
D．on ; at
