Correct Answer - D
Frequencies of closed pipe: `200, 600, 1000`, ….
Frequencies of open pipe: `200, 400, 600, 800`, …
(i) First overtone is `600 Hz` for closed pipe, `400 Hz` for open pipe, (i) is wrong
(iv) `600 Hz` is first overtone of closed pipe, second overtone of open pipe, (iv) is `O.K`.