To verify that a value is a root of a function we use the following setup
F(x) = 0 and replace x by the value in this case 3 and -i.
Let's begin with x=3




Only options C and D pass the first filter.
Let's apply x=-i to those options




both of the accomplish the equality f(x)=0
So to finish we replace the point to check which functions pass
Replacing f(1) = -16

This is equals to -16

So the answer is option C