Electromagnetic waves are often distinguished from mechanical waves. The distinction is based on the fact that electromagnetic waves . *

A)can travel through materials and mechanical waves cannot
B)come in a range of frequencies and mechanical waves exist with only certain frequencies
C)can travel through a region void of matter and mechanical waves cannot
D)electromagnetic waves cannot transport energy and mechanical waves can transport energy

The  answer is electromagnetic waves can travel through a region void of matter and mechanical waves cannot (option C)

Explanation:

To begin with, electromagnetic waves are waves that are created due to vibrations between a magnetic and electric field. On the other hand, mechanical waves are waves that are created due to vibration in matter or energy transfer through a material medium.

Electromagnetic waves are quite distinct from mechanical waves because the latter requires a material medium to transport energy while the former does not. In fact, electromagnetic waves can carry out transportation of energy through the vacuum of outer space.

there are no correct statementd on the list of choices you provided.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.