The correct option is A 350ms−1
Answer is A.
If we increase the temperature of the air, then the speed will increase.
For every one degree Celsius rise in temperature, the speed of sound increasesby 0.6 m/s.
The speed of sound at 20 degrees C is 340 m/s.
So, the speed of sound at 30 degrees c will be around 350 m/s.