Directions: In the question below, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option:
Assertion (A): The quadratic equation $x^2 - 6x + 9 = 0$ has real and equal roots.
Reason (R): A quadratic equation $ax^2 + bx + c = 0$ has real and equal roots if and only if its discriminant $D = b^2 - 4ac = 0$.