The speed of light in four different materials is shown below:

material speed of light in thousand miles per second
a 140
b 78
c 186
d 124

which material is the most dense?
material a
material b
material c
material d

Are the earth's ocean floor and continents the same age geologically? why or why not?

The picture represents a structure of the respiratory system. which is the function of this structure? to bring air into the body to exchange oxygen with carbon dioxide to carry air to the lungs to release oxygen from the body

Moving down the ramp from 6 meters to