先知道下英语倍数表达法,此题中主要还是第一点比较重要
用英语表达“A是B的N 倍长（宽，高，大，重等）”，“A 比B长（宽，高，大，重等）N 倍” 或“A 的长度（宽度，高度，大小，重量等）是B的N倍”，可用下列几种句型。

　　1.“A + be + 倍数 + as + 计量形容词原级 + as + B”

　　This tree is three times as tall as that one. 这棵树是那棵树的三倍高。

　　His father is twice as old as he. 他父亲的年纪有他两倍大。

　　2.“A + be + 倍数 + 计量形容词比较级 + than + B ”

　　The Yangtze River is almost twice longer than the Pearl River.

　　长江差不多比珠江长两倍。

　　The dictionary is exactly five times more expensive than that one.

　　这本字典比那本恰好贵5倍。

　　3.“A + be + 倍数 + the + 计量名词 + of + B ”

　　The newly broadened square id four times the size of the previous one.

　　新扩建的广场是未扩建时的四倍大。

　　4.“The + 计量名词 + of + A + be + 倍数 + that + of + B ”

　　The size of the newly broadened square is four times that of the previous one.

　　新扩建的广场为以前的四倍大。

故本题选B,省略了twice as long (as it)