逐架放煤达到要求，及时升起（）并打出插板。
A.前梁
B.尾梁
C.前柱
D.后柱
参考答案：B
A dream is to a man________wings are to a bird.If you have no dreams,your future is empty. [ ]
A. where
B. what
C. that
D. which
晶体的对称要素包括对称面，对称轴和对称中心.
