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【判断题】
渗碳体是碳的化合物,其符号为Fe3C,性能特点是硬度高,脆性大,塑性、韧性几乎为零。( )A.
正确
B.
错误
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皮皮学刷刷变学霸
举一反三
【单选题】在使用显微镜观察标本时，需要从侧面看着物镜并旋转粗准焦螺旋，将镜筒下降。从侧面看着物镜的目的是（）
A.
防止污染镜头
B.
防止物镜碰到玻片，造成损伤
C.
使物像对准光源
D.
使物镜降到能看清物像
【单选题】______ is discussed at the meeting must be kept secret.
A.
What
B.
That
C.
Which
D.
Whether
E.
When
【简答题】Implementation of the meeting must be pursued with vigor.
【单选题】of them has arrived yet. So I'm afraid that the meeting must be held next time.
A.
All
B.
None
C.
Each
D.
Either
【单选题】What she( ) to us at the meeting must be true .
A.
announced
B.
announces
C.
announce
D.
announcing
【单选题】The meeting must be held before Wednesday, because John is _______leave on Thursday.
A.
arranged about
B.
scheduled to
C.
planning for
D.
being about to
【单选题】The meeting must be held before Wednesday, because John is _____ leave on Thursday.
A.
arranged about
B.
scheduled to
C.
planning for
D.
be about to
【简答题】如图为显微镜结构图，请据图回答下列问题．在【】内填字母，横线上写结构名称 （1）对物像具有放大作用的是[______]______和[______]______． （2）能较大范围地升降镜筒的是[______]______． （3）能反射光线的是[______]______．（4）观察时把玻片放在[______]______，并用[______]______压紧玻片．使要观察的标本对准[_____...
【单选题】在使用显微镜观察标本时,需要从侧面看物镜并旋转粗准焦螺旋,将镜筒下降。从侧面看物镜的目的是:
A.
使物镜降到能看清物像
B.
使物像对准光源
C.
防止物镜碰到玻片,造成损伤
D.
防止污染镜头
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