Explain

@alva, For each of the choices, domestic call between 9-5 pm = class that involves extensive lab work, calls at any other time = class that does not involve extensive lab work, cost 15 c = conducted in the laboratory, cost 10 c = conducted in a normal classroom. So the conclusion we are looking for is - any class not conducted in a normal classroom, is conducted in a laboratory (choice E). The issue with (B) is that the first part of (B) parallels the argument in the stimulus, but the conclusion is different. The conclusion in (B) - if a class is not conducted in a normal classroom, it will involve extensive lab work is equivalent to - if a phone call does not cost 10 c a minute, then it is starting between 9 am and 5 pm. While this conclusion is not necessarily wrong, we are looking for an answer choice that most closely parallels the reasoning in the stimulus, and (E) is the perfect fit. Does this make sense? Let me know if you have any further questions.