Question

many roller coaster riders dont even realize that as theyre cruising down the track at 60 miles per hour, there is no engine in the roller coaster. the car is pulled to the top of the first hill when the ride begins, but after that the coaster runs completely on its own. it all happens with the conversion of potential energy to kinetic energy. once the coaster descends the first hill, it has all the kinetic energy it needs to drive the roller coaster. different types of wheels keep the ride running smoothly and guide the coaster on the track. when the ride comes to an end, compressed air brakes stop the roller coaster.
its safe to say that most people riding a roller coaster have no idea who invented them, their history, or their mechanics. all they know is that they better hold on for the ride of a lifetime!
what is paragraph three mostly about?
roller coasters are equipped with different wheels to perform specific functions.
roller coasters operate without a motor.
roller coasters are stopped with compressed air brakes
once the coaster goes up the first hill it has all its momentum.

Explanation:

The first paragraph explains that the roller - coaster has no engine. It is pulled to the top of the first hill at the start, and then runs on its own. This indicates that it operates without a motor. The other options are details (wheels, brakes) or incorrect statements (momentum is related to motion, not just going up the first hill).

Answer:

Roller coasters operate without a motor.