Comparing text in a text box is almost impossible.
You would be better off making it a multiple choice quiz.
Set a text box like this:
Text "What color is the sky?"
Text "A=Blue B=Green C=Yellow"
Global Variable RightAnswer=0 WrongAnswer=0
On keyboard A key pressed set RightAnswer =1
On Keyboard B pressed WrongAnswer =1
On Keyboard C pressed WrongAnswer =1
On RightAnswer =1 go to next question
Something like that.