A. Tell whether the given rule describes a function or not.
1. The rule which assigns to each car its plate number.
2.The rule which assigns to a number an integer greater than it.
3. The rule which assigns to each person his aunt.
4. The rule which assigns to a finite set the number of elements in it.
5. The rule which assigns to each natural number its additive inverse.
6. The rule which assigns to a positive number whose square is the positive number.
7. The rule which assigns to each polygon its number of sides.
8. The rule which assigns to each student his teachers.
9. The rule which assigns to each person his birth month.
10. The rule which assigns to each month the person having that as birth month. ​