You may take a look at our iPhone/iPad app, GMAT ToolKit
(#1 GMAT Prep app in the App Store). The app gives you the right answer and explanation once you submitted your answer choice for each question. It's like what you are looking for.
HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame