is a change in the position of a body with respect to time relative to a reference point.

Velocity

Explanation:

Velocity is a vector quantity which is defined as the rate of displacement. Displacement is also a vector quantity which is measured as the shortest distance between the final point form the reference point.

Velocity is negative when the displacement is negative, displacement can be negative if taken in opposite direction form the desired direction with respect to the initial point.

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.

there are no components of a physical goal mentioned on the list of choices that you've provided.