1. Which of the following is true about sound waves? They move faster than light.
They make wind.
They vibrate the air.
They move slower in water than in air.

They vibrate the air.

Explanation:

The sound waves in air are longitudinal while the light waves are transverse Sound wave is longitudinal because the medium particles move parallel to the direction of wave propagation, whereas a light wave is transverse because the medium particles move perpendicular to direction of wave propagation. Hence, option C is correct.

cell differentiation  is how generic embryonic  cells  become specialized  cells. this occurs  through a process called gene expression. gene expression is the specific combination of genes that are turned on or off (expressed or repressed), and this is what dictates how a  cell  functions.

explanation:

there are no contact forces mentioned on the list of choices that you've provided.