B. Is the correct answer.
Sam and Jenny ride their bikes at a constant velocity of 3 miles per hour.
Explanation:
Here we see that both of them are moving at a constant velocity which means their speed is constant and they are moving in a straight line.
Zero acceleration is implied on the bikes and the net force is BALANCED.
When forces are in balance, acceleration is zero. Velocity is constant and there is no net or unbalanced force.
Pangea was the supercontinent that had all the landmasses of earth together before the Triassic period and that broke up into Laurasia and Gondwanan. However, Panthalassa is a prehistoric ocean that was surrounding Pangea.
Hope this helps!