Which state of matter has properties that are responsible for your smelling the perfume of someone across the room?
A. Gas
B. Solid
C. Liquid
D. Plasma

Gas

Explanation:

Solid particles cannot travel far, since they are mostly attracted together.

Liquid Particles cannot travel far either, although they can flow, but they flow with respect with gravity.

Plasma... is a very hot material, it's probably cooler than the sun but it's way warmer than your average boiling water.

So which leaves gas, since we know that the properties of gases are :

Gas particles can freely travel

Gas particles are spread out

These enables it to flow around the room, and this has something to do with diffusion, but i believe it's out of topic.

So, the answer's gas!

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.