The correct answer is B. Medium. This is because to travel through the ear, the sound wave must go through the ear drum.
Earthquakes, specificaly the threat of the san andreas fault
Formula for speed of light is:

Where:
c=speed of light = 300000 km/s
d=distance
t =time
Rearranging formula for t and calculating:
Answer:
Salinity and temperature can alter seawater density.
Explanation:
If there are more ions of salt in the seawater, the mass is increased and the volume is the same, then the density increase.
The density decreases when temperature is increased. And salinity affects the freezing point too.