下图主板接口中,①处是 (28) ,②处是 (29) ,③处是 (30) 。[*]
A.PS2接口 B.USB接口 C.音频接口 D.网络接口
参考答案:A
Mary was much kinder to Jack than she was to the others,______, of course, made all the others upset.(2011·北京)
A.who
B.which
C.what
D.that
计算题:有一内径为25mm小管,管中流速为1.0m/s,水温为20℃,求管道中水的流动类型?(已知20℃水的粘度为1CP,密度为998.2kg/m3。)