Your students have already finished a Test/Quiz, but you want to make the Test available again for just one student for a make-up.
The easiest way to make a quiz available to just one student is to set a password on the quiz and give it only to that one student, as follows:
1. Make sure the student doesn't already have a grade or a lock for the Test/Quiz in Control Panel > Gradebook. If so, clear the grade/lock by clicking on it.
2. Go to Control Panel > Quizzes > Modify > Modify the Test Options.
3. Make the quiz available in the usual way using "Make the link available" = "yes".
4. Remove any date restrictions on the Test link by checking the "Display After" date is in the past and the "Display Until" date is in the future.
5. Scroll down to "Password. Require a password to access this Test." Check the box, invent a password and type it in the box.
6. Click Submit at the bottom.
7. Give the password you invented to the one student so only that student will be able to enter the quiz again, verbally or via Email / Message.
Once the student takes the make-up Test/Quiz, you can confirm the grade in Control Panel > Gradebook and then make Test link unavailable again.