How does the sound propagate?

Question: How does the sound propagate?

Options:

In waves
In rays
Only through materials
Only through the air

Correct answer:

In waves

Other game answers:
Find the answers to guess the gif, logo quiz 2015, emoji puzzle and emoji nation.
You can find other questions and answers of trivia crack at triviacrackcheats.org (other languages are also available, for this game).