If the length of a vibrating body increases, the frequency of vibration decreases.
If the length of a vibrating body decreases, the frequency of vibration increases.
As the length of 30 cm scale is smaller than that of 60 cm, the 30 cm ruler will vibrate faster and the frequency of vibration will be more as compared to another ruler. Hence, the pitch of the sound produced is high.
Therefore, only statements-ii and iv are correct.