There are 3 different types of Competitions.
First X Winners.
You can choose the amount of customers that you would like to be winners i.e. The first 5 or first 20 are winners.
Correct/ Incorrect Answers
You can create a competition that involves correct and incorrect answers, where you can specify answers for both categories. From there you can randomly generate winners with the correct answers.
Any Answer Can Win
You can create a competition asking customers to answer a question, and allow any answer the chance to win.