How to select random questions from a text file?

I'm going to write a quiz game. I have a txt file full of questions and answers. Each question is in a different row and has a difficulty level (1-10) (not sorted). I want to read in and store them in an array. (I did a question structure). My question is: How should I read in to an array randomly? A question's index would be its difficulty level-1.

Thanks for your answer in advance.