加湿器在使用前须将储水器加注（）。
A.自来水
B.凉开水或蒸馏水
C.温水
D.冰块
参考答案：B
We confirm ____ purchased 2,000 MP3 Players ____ you.
A. have, to
B. having, from
C. to have, from
D. have been to
液压系统引起爬行主要影响工件的表面粗糙度。
