闸阀的阀杆分为（）.
A.明杆和暗杆
B.明杆楔式弹性闸板
C.明杆平行式单闸板
D.明杆平行式双
参考答案：A
若集合M={1，m2}，集合N={2，4}，M∪N={1，2，4}，则实数m的值的个数是 [ ]
A.1
B.2
C.3
D.4
This is Mr. Smith, ______ I think has something interesting to tell us. [ ]
A. who
B. whom
C. that
D. 不填
