下列化学品中没有抗氧化作用的是（）。A、I-245 B、LPO C、PS-800 D

如图所示为一列向右传播的简谐横波在某个时刻的波形，由图像可知(　　)．

A．质点b此时位移为零

B．质点b此时向－y方向运动

C．质点d的振幅是2 cm

D．质点a再经过通过的路程是4 cm，偏离平衡位置的位移是4 cm

27. As five children under 10 got drowned in a southern province, it is not socially _____ for

parents to leave children unattended at that age.

A．acceptable

B．affordable

C．sustainable

D．believable

There are so many kinds of MP4 players in the shop. I can't decide ________. [ ]

A. what to buy

B. which to buy

C. when to buy

胰腺癌最好发的部位是（）。

A.胰头部

B.胰腺体部

C.胰腺尾部

D.各部分发生率基本相同

E.异位胰腺

( )是现代人事行政制度的基础。

A．绩效考核制度

B．职位分类制度

C．人事激励制度

D．工资福利制度