How to find the parimeter of a semicircle?

Question: How to find the parimeter of a semicircle?

(1)1/2 (πd) + d or πr + 2r

(2)1/2πr²

(3)1/3π²r

(4) none of these

Answer (1) is absolutely right answer because we know that the formula of the perimeter of semicircle is 1/2 (πd) + d or πr + 2r.