________ modeling business is by no means easy to get into, the good model will always be in demand．
A.WhileB.SinceC.AsD.If在线课程A
解析：
解这道题，关键要搞清主从句的逻辑关系。从句modeling business is by no means easy to get into和主句the good model will always be in demand不是因果关系，也不是条件和结果的关系，而是表示表示让步。连词while可以引出让步状语从句。大意是：“尽管模特行业很难进入，但好模特总是供不应求。”