1-6. In the face of widespread concern about environemntal waste, compact disc manufacturers are attempting to find a repalcement for the disposable plastic box in which they package their product.

athe disposalble plastic box in which they
B. the disposable plastic box where they
C. a disposable plastic box in which to
D. disposable plastic boxes inside which they
E. the disposable plastic boxes in which to

答案：A

请问，a ,e的区别在哪里？e为何错误?

I see, many thanks !!!