I want to know if there is an app where I can load question and answers for my students to practice what they have learnt in form of multiple choice question and answers.
There are plenty applications already created and available for your inquiry. These apps are called Quiz Makers and there are plenty to download from. I recommend checking the database of Software Informer. I have already narrowed down the result list to display only what's relevant for your inquiry.
Search results list: http://software.informer.com/search/quiz+maker
Use any application from the list to create quizzes with question and answers.