倍数句型：
(1)倍数+比较级+than...，
例：The room is twice larger than that one.这个房间是那个房间的两倍大。
There is 30 times greater chance of being hit by lightening than being attacked by a shark.
(2)倍数+as+原级+as...，
例：The room is three times as large as that one.
这个房间是那个房间的三倍。
(3)倍数+the size /height/length /weight /width of...
例：The room is three times the size of that one.这个房间是那个房间的3倍大
should have done =ought to have done本应该做而没做