Bats use sound waves to determine the location of insects that are flying at night. What is the primary medium that the bat's waves travel through?
A. Air
B. Trees
C. Clouds
D. The ground

Answer :

pegah
The answer is A. Air 
because our sound travel in the air so bat`s waves should travel in the air to find the insects that are flying in the air! :)))
i hope this is helpful
have a nice day