Answer:
C
Explanation:
You have done it correctly.
The two binomials multiplied together are
(x + y)(x + y) which equals x^2 + xy + xy + y^2 which is x^2 + 2xy + y^2 or your given.
When you add the two binomials, you get
x + y + x + y = 2x + 2y
The answer is C just as you have indicated. Good job.