一般直径在200mm以上的电机转轴宜采用( )轴。
A．锻造
B．圆钢
C．焊接
D．空心
参考答案：A
用所给词的适当形式填空。
1. Today we are _________ (put) up the Christmas tree.
2. Yesterday we _________ (buy) gifts.
3. Would you like to help _________ (we) put up our Christmas tree?
4. This is a little pair of _________ (skate).
5. These are two toy _________ (snowman).
水泥砂浆的保水率宜（）
A.≥80%
B.≥84%
C.≥88%
D.≥92%
