The way I see it is if the correct answer is A because it strengthens the conclusion, well so it should be true as well and the answer A will be the assumption that the author bases his conclusion on.
I think you cant mix up the three questions... If you consider must be true questions
, the correct answer choice allows no external information
to be used apart what is stated in the premises of the argument. any answer choice that uses external information is bound to be wrong.
In both strengthen and assmumption questions
, the correct answer choice
takes the liberty of using external information. you dont have to think whether these assumptions are really true or not. assumptions are just assumptions , if they are true , then they are not assumptions. hope this helps..