You can have a Question object with the following attributes:
1) QuestionText
2) QuestionChoices (with choices)
3) SingleChoice (yes, no)
4) CorrectAnswer
You will also need the QuestionAnswer object with the following attributes:
1) Reference to the corresponding Question object
2) Answer
This object will have two forms - the first will show the text of the question and a single choice (yes, no) - this is if the SingleChoice flag is yes. The second form will show a choice list of possible answers as checkbox list
The admin. will just populate the instances of this Question object.
Then you need a process that would find all relevant instances of the Question object and for each Question create a QuestionAnswer and display the appropriate form - one by one.