Instead of testing the assertion and reason separately, link them through what actually happens when wheat flour is kneaded with water. Two proteins, gliadin and glutenin, hydrate and combine to form gluten, a network that traps gas and stretches without tearing, giving dough its binding and stretchy feel described in Assertion (A). Because Reason (R) names this very protein as the cause, it is not just a true statement standing beside (A), it is the mechanism behind (A). \[\boxed{\text{Both correct, R explains A}}\]