即将一战，问比较的问题，大家帮帮忙

prep-2-147

its number are now five times greater than when the use of DDT was sharply restricted in the early 1970's

难道大家觉得这句话没有什么不对吗（这是正确答案）number  的比较对象不对称呀，实在是疑惑

大家能给解释一下吗