请教大全最新真题 15-10，多谢！

(A)    Because they desire to be as thin as possible, young female ballet dancers and gymnasts sometimes fail to maintain good eating habits.

(B)    Young female ballet dancers and gymnasts sometimes fail to maintain good eating habits because they desire to be as thin as possible.

正确答案是A，但是B有何不对？

请高手指教！

还是不太明白！

不过现在看看，会不会是句子中心的问题。A的中心是原因，而B的中心是结果。