薄透镜组有哪些像差特性？

The experiment shows that proper amounts of exercise,if _____ regularly,can improve our health.   [    ]

A. being carried out                            

B. carrying out  

C. carried out                                  

D. to carry out

A quality assurance team should be（ ）.①associated with any particular development group②depended upon any particular development group③responsible for reporting directly to management④in-depended upon any particular development group

A．①②

B．②③

C．③④

D．①②③④

适用于主进风道的防爆配电装置类型为( )。

A．气压型

B．防爆型

C．正压型

D．增安型

综合书店，是指经营的（）广泛，品种较全的书店，一般有大、中、小型之分。

下列哪种体征提示有心脏压塞

A．水冲脉
B．脉压增加
C．低血压
D．心包摩擦音
E．心包叩击音