Implement the MultiChoiceQuestion class described in Exercise E9.5 of your textbook.

Only override addChoice and display.

For the final version, complete the method readQuestions that reads a sequence of Question, ChoiceQuestion or MultiChoiceQuestion from a file. The question text is on the first line, followed by either

1. a single line, in which case that is the answer to the Question
2. more than one line, exactly one of which starts with a *, in which case those are the choices for a ChoiceQuestion
3. more than one line, of which more than one starts with a *, in which case those are the choices for a MultiChoiceQuestion