This is a weird question. The mark of a "strong" acid is that it completely dissociates in water, i.e. it will be essentially be present in water as H+(aq) (actually hydronium) and the appropriate anion. The only problem anyone could have with B is that it dissolves more than "well"... C is odd because the ammonia could make an acid that isn't strong dissolve really well. It obviously doesn't affect a strong acid adversely with respect to dissolving. As for A: a weak base can have an acid that isn't "strong" as it's conjugate. The conjugate of a strong acid is very very weak.
