Two triangles, △ABC and △DEF, are right–angled at A and D respectively. If BC=EF and AB=DE, which of the following statements is true?
(a) They are congruent only if AC=DF is also given.
(b) They are only similar; congruence cannot be established with the given information.
(c) No further information is required; the triangles are congruent by RHS criterion.
(d) They are congruent only if ∠B=∠E is also given.