Here's a problem to solve: A student compared the speeds at which a large and a small marble rolled down an inclined plane. In order to make the findings more reliable, the student should

Among the 4 following options, which is the correct answer?

- A: release the marbles at different heights.
 
- B: repeat the experiment several times.
 
- C: tilt the plane at different angles.
 
- D: use two marbles that are the same size.
 