Define the independent and dependent variables:

A researcher was interested in finding out if type of learning was related to class performance. She randomly assigns 100 General Psychology into 1 of 2 groups: 50 students use computerized instruction exercises; the other 50 spend an equal amount of time reviewing the text and lecture notes. At the end of the semester the researcher compares final exam scores in both groups.

d is the correct answer

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.

the correct answer is "inertia"