Answer: D.-6 and F.3
Explanation:
The given rational number :

To find : The value of x , where the rational expression becomes equal zero.
Let's check all the options :
A. 7
At x= 7 ,

B. -7
At x= 7 ,

C. 6
At x= 6 ,

D. -6
At x= -6 ,

E. -3
At x= -3 ,

F. 3
At x= 3 ,

Thus, at x= -6 and 3 , the rational expression equals to zero .
So , the correct options are : D.-6 and F.3