No ones face is perfectly______. For example, one eyebrow is often slightly higher than th

接触粉尘1～2年发生的硅沉着病，属何种硅沉着病

A.硅沉着病

B.晚发性硅沉着病

C.硅酸盐肺

D.肺尘埃沉着病

E.速发性硅沉着病

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Tom was very lucky______with his life: he almost did not get out of the room.

A．escaping

B．to escape

C．to have escaped

D．to be escaping

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Betty is the only one of the students who______to represent the group.

A．have been chosen

B．has been chosen

C．have chosen

D．has chosen

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对k个处理组，b个随机区组的资料进行方差分析，其误差的自由度为

A、kb-k-b

B、kb-k-b-1

C、kb-k-b-2

D、kb-k-b+1

E、kb-k-b+2

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