To complete the square, how do you find the value that must be added to the expression to make a perfect square trinomial? What is the value?

x2 +
2
5
x + ?
A) square
2
5
and add to both sides;
4
25
B) take half of
2
5
and add to both sides;
1
5
C) square half of
2
5
and add to both sides;
1
25
D) take half of
2
5
and add the opposite to both sides;
−1
5