Which statement is correct about the rotational inertia of a rotating object? A) Rotational inertia is conserved because it is resistance to change in rotational motion.
B) Rotational inertia is always decreasing because angular momentum is conserved.
C) When mass moves closer to the point of rotation, rotational inertia decreases.
D) When mass moves closer to the point of rotation, rotational inertia increases.

b.transmitters send radio waves, and receivers capture radio waves.

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.