Had to look for the options and here is my answer. What happens when the fluid discharge of an air-operated reciprocating pump is shut, this will cause the pump to OVERSTROKE. Overstroke happens when the engine is switching in a normally-closed manner.
An atom would be your answer, so B!
The part that it played was in the changing of the environment/climate for the organisms that live on those continents. And the part it could've played was the way that the organisms had to adapt to that climate and it stayed that way over generations.
