How can i get a random line from a text file in sml ? How to make a multi choice question program in sml?

I want to make a multi choice question program in SML.

I have a text file whose content is structured as follows:

category1:Basic sml/sql
1-How many subsets does the power set of an empty set have?
A) One
B) Two
C) Three
D) Zero
Ans:A
2-What is the cardinality of the set of odd positive integers less than 10? 
A) 20 
B) 3 
C) 5 
D) 10 
Ans:C

Each category has more than 5 questions

Each question belongs to a category

For each question there are 4 proposed answers followed by the answer on another line

I would like, to be able to retrieve and display to the user just the question (a random question) and the corresponding proposed answers. I have written this function that allows me to retrieve line by line all the content of my file. But I'm still stuck on how to unload a question-answer block.

fun getFromFile(file_name) =
    let 
      val file = TextIO.openIn file_name
      val text = TextIO.inputAll file
      val _ = TextIO.closeIn file
    in
      String.tokens (fn c => c = #"\n") text
    end
    
val table = getFromFile("question_file.txt");

How could I proceed? Is it possible to retrieve the lines of the file without passing them through a table first (retrieve the text directly)?