What is the purpose of the coils under a refrigerator? they release extra refrigerant that may have built up over time. they release thermal energy generated by the motor to keep the refrigerator cold. they keep the inside of the refrigerator cool.

Sometimes it's hard to tell which choice the question wants you to pick, because all the choices on the list are a little bit whacko.

I think this question is fishing for the second choice: "They release thermal energy generated by the motor to keep the refrigerator cold."

But that's really a somewhat misleading statement.  The thermal energy you have to deal with in a refrigerator is NOT GENERATED BY THE MOTOR.  It's the heat REMOVED from inside the refrigerator.  Once it's removed from the food in there, you've got all this heat and you have to DO something with it.  The coils (usually on the back of the refrigerator, not the bottom) release the heat that was removed from the food and the air inside.

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees.