Answer:
<u><em>A. wavelength</em></u>
Explanation:
The others are about sound and how high it is. That has nothing to do with time.
Time = (distance) / (speed)
= (30 km) / (30 m/s)
= (30,000 m) / (30 m/s)
= (30,000 / 30) sec
= 1,000 seconds
= 16 minutes 40 seconds
The answer is C. <span>Light travels at different speeds in water and in glass.</span>