In refraction, when a wave travels from one medium to another, it
a. changes speeds.
b. stays in step.
c. always moves in the same direction.
d. travels in the opposite direction.

The correct option is A.

Explanation:

Refraction is the phenomenon in which there is a change in the direction of the light wave when it passes from one medium to another.

It is caused due to the change in the speed of the wave.

Refraction phenomenon occurs in the lens.The light ray is refracted when it passes through the lens.

Therefore, when a wave travels from one medium to another, it changes the speed.

radiation

explanation:

heat is transmitted by radiation

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.