Sound waves cannot travel in
a. steel.
b. air.
c. a vacuum.
d. water. e. sound can travel in all of the above.

The answer is D.  A Vacumn

Explanation:

Sound cannot travel through a vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in.

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.