In analyzing this diagram, which statement represents a crucial step to proving the pythagorean theorem using this diagram?
A) The large square on the left contains two smaller squares
B) The large square on the right contains a smaller square with side length c
C) The perimeter of the blue square is equal to the perimeter of the yellow square.
D) Recognize that BOTH of the large squares contain 4 right triangles with base a and height b