What would the canoe do if a person were in the canoe on a calm lake and they threw a heavy stone into the water in front of them?
the canoe would move forward a bit.
the canoe would move backward a bit.
the canoe would move forward and keep going.
the canoe would remain still because it is too heavy.

When you throw the stone forward, you create some momentum forward. In order to conserve momentum, there has to be some momentum backward. The canoe moves backward, and keeps going.

i think the answer is a and b

i wish you luck

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.