Shown here are the three essential steps in a proof of the Pythagorean Theorem. Which statement is justified by the diagram in Step 1?

A) 4(
AB
2
) = C2
B) B(A + B) = B2 + 2(
1
2
BA)
C) A2 + B2 = C2
D) (A + B)2 = A2 + 2AB + B2