Ahmed saw all of these things as he walked to school this morning. Which one is an example of a force pushing downward toward the ground?
A. A bird sat on a telephone wire.
B. A woman moved her child from one place to another in a wagon.
C. A man pulled weeds in his garden
D. A dog tugged on a rope a child held

where's the following? you gotta add it to know what the choices are

explanation:

if they have a finite resultant

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.