题干
.
Would it be ________ for you to pick me up at four o’clock and take me to the airport?
Would it be ________ for you to pick me up at four o’clock and take me to the airport?
A：free
B：vacant
C：handy
D：convenient
答案(点此获取答案解析）
D
．让圆环沿杆滑下，滑到杆的底端时速度刚好为零．则在圆环下滑过程中
