Air pollution in the city had reached four times the acceptable levels.
这座城市的空气污染程度曾高达可接受标准的四倍。
《牛津词典》
2
It can inflate (使膨胀) itself with water and air to turn into a ball several times of its real size.
河豚可以利用水和空气使自己膨胀，变成一个等于其数倍实际大小的球。
3
Even Tommasini, who had advocated Gilbert's appointment in the Times, calls him "an unpretentious musician with no air of the formidable conductor about him".