选：A
倍数表示方法
a. 主语+谓语+倍数（或分数）+ as + adj. + as.例如
I have three times as many as you. 我有你三倍那么多.
b. 主语+谓语+倍数（分数）+ the size （amount,length…） of….例如：
The earth is 49 times the size of the moon. 地球是月球的49倍.
c. 主语+谓语+倍数（分数）+ 形容词（副词）比较级+ than….例如：
The grain output is 8 percent higher this year than that of last year. 今年比去年粮食产量增加8%.
d. 还可以用by+倍数,表示增加多少倍.例如：
The production of grain has been increased by four times this year. 今年粮食产量增加了4倍.