1.介词 + 动名词(doing)
简单介词:
1.表示地点:at ,in, on, to, above, over,below, under, beside, behind , between
2.表示时间:in , on,at, after, from, since for, behind
3.表示运动:across, through, past, to, towards, onto, into, up, down
4.表示进行:at, under, on
5.表示其他:on, about, by, w