Answer:
D
Step-by-step explanation:
So, let's say that we have the following equation:

And we want to complete the square.
What we need to do is to divide the coefficient of x by half. Square that. Then add that number to both sides.
The answer that reflects this is choice D.
For instance if we have:

Divide 4 by 2 and then square it.
4/2 is 2. 2²=4. Add 4 to both sides. Thus:

And now, we can complete the square:
