The zeros of the function f(x)=x^{2}-a x+2 a are integers. What is the sum of the possible values of a ?

**Answer Choices**

A. 7

B. 8

C. 16

D. 17

E. 18

The zeros of the function f(x)=x^{2}-a x+2 a are integers. What is the sum of the possible values of a ?

**Answer Choices**

A. 7

B. 8

C. 16

D. 17

E. 18