(DUE TODAY) The Pythagorean theorem states that the sum of the squares of the legs of a right triangle is equal to the square of the hypotenuse. Margaret uses this theorem to simplify and rewrite the expression (b/r)^2 + (a/r)^2 using the triangle shown above. Which trigonometric identity can she prove with her expression?

A. 1 + tan^2θ = sec^2θ
B. sin^2θ + cos^2θ = 1
C. csc^2θ + sec^2θ = 1
D. 1 + cot^2θ = csc^2θ