請教verbal review #72

The gyrfalcon, an Arctic bird of prey, has survived a close brush with extinction; its numbers are now five times greater than when the use of DDT was sharply restricted in the early 1970's.
(A)extinction; its numbers are now five times greater than
(B)extinction; its numbers are now five times more than
(C)extinction; their numbers now fivefold what they were
(D) extinction; now with fivefold the numbers they had
(E)extinction; now with numbers five times greater than

答案是A 我不懂A跟B的差別
我看過詳解 它是說如果用MORE是指more number 而不是 more gyrfalcon 我不太了解 為什麼它會知道用GREATER 就是指修飾gyrfalcon呢? 是句意還是文法問題呢?可否請大牛們幫忙一下???

more number means more catergories, which is different from greater number as we usually use, which means gyrfalcon here. 

Anyway, in this context, more number in B is wrong.

can you explian more about the difference between " more " and : greater"?? I still do not get your point.