( )是机器的运动单元。
A.零件
B.构件
C.机构
D.部件
参考答案:B
解析: 构件是机器的运动单元或运动整体。构件可以是一个零件,也可以是几个零件的刚性组合。
若U=Z,A={x|x=2k,k∈Z},则CUA=______.
In the reading room, we found her ________ at a desk, with her attention ________ on a book.
A.seating; fixing
B.seated; fixed
C.sitting; fixing
D.to sit; fixed