题干
I'd ______ the operation unless it is absolutely necessary.
A：rather not have
B：rather not to have
C：not rather had
D：rather not having
答案(点此获取答案解析）
A
t时间内平均速度为v/2，后
t时间内平均速度为2v，则物体在t时间内平均速度大小是( )
