#### Answer

a. Function
b. Not a function
c. Function
d. Not a function

#### Work Step by Step

a. Every piece of A is matched with only one piece of B. So, it is a function.
b. 1 in A is matched with both -2 and 1 of B. So, this is not a function.
c. Every piece of A is matched with only one piece of B. So, it is a function.
d. 2 in A is not matched with a value in B. So, this is not a function.