I need an app that has a question that the participant has to answer.

You can create a Sweepstakes that will provide you an option to have customized questions that the user can answer.  You can choose the following question formats:

1. Allow user to type text in text box.
2. Choose an answer from the drop down.
3. Select one of the answers listed using radio buttons.
4. Choose multiple answers using check boxes.
5. Choose Trivia, this would allow you to specify the correct answer among the options provided to the user.

You can also make the question compulsory or optional.