Hey there!
The answer would be B. The sound moves from air to water.
Sound travels through different mediums. It goes fastest in solids, a little slower in liquids, and slowest in air. Sound is a very fast wave, but remember that mediums can differ that. In a vacuum space, there is no sound at all. (ex. outer space)
Hope this helps !
1. Physical size of Russia compared to other countries, despite a lack of visible borders from space.
2. Part of Russia's outline would likely be obscured by the various clouds and objects in the stratosphere; this would allow the astronaut to view potential cloud and weather patterns on earth.
3. An astronaut could see outlines of Russia's geography such as mountain ranges.
Hope that it helps :)
I believe it would be 2m/s.
The best frequency should be 70 Hz you simply find the difference between 280 Hz and 210 Hz
