—_____ is his hair?
—It's black.[ ]
A. What class
B. What grade
C. What color
D. Where
答案:C
发动机的有效扭矩为890N.m,曲轴的转速为1200转/分,求发动机的有效功率。
人工推车,滑行速度不得大于()m/s。
A.3
B.5
C.7