求解释，GWD里的题目

寻沫访华

?As it is with traditional pharmacies, online drugstores rely on prescriptions to be successful, since it is primarily prescriptions that attract the customers, who then also buy other health-related items.

?A.As it is with traditional pharmacies, online drugstores rely on prescriptions to be successful

?B.As with the case of traditional pharmacies, online drugstores rely on prescriptions to have success

?C.As is the case with traditional pharmacies, prescriptions are the cornerstone of a successful online drugstore

?D.As traditional pharmacies, so online drugstores rely on prescriptions to be successful

?E.Like traditional pharmacies, the cornerstone of a successful online drugstore is prescriptions

求解释，答案为什么是C呀

寻沫访华

谢谢你，知道了

liulujun

as is 意思是 ‘正如’，是非限制性定语从句... 并不是倒装...可以当成一个固定句型记者...