While some academicians believe that business ethics should be integrated into every business course, others say that students will take ethics seriously only if it would be taught as a separately required course.
(A) only if it would be taught as a separately required course
(B) only if it is taught as a separate, required course
(C) if it is taught only as a course required separately
(D) if it was taught only as a separate and required course
(E) if it would only be taught as a required course, separately
我的印象中if only引导的条件状语从句要用虚拟语气，即would,could之类，有这样的规则吗？根据这条规则，我首先排除了b,请nn帮忙解释一下阿 | 
