How do collisions between molecules transfer energy from a system of reacting substances to its surroundings?

Question

A.) They cause heat to flow from the system to the surroundings.

B.) They cause the thermal energy of the surroundings to decrease.

C.) They cause the potential energy of the system to increase.

D.) They cause the molecules to flow into the system from the surroundings.

My guess is D, but I'm not sure.

EDIT: The answer is D. They cause molecules to flow into the system from the surroundings. :)

Answer 1

No, it's A. Energy is transferred as heat outflow, not by inflow of the surroundings! Please suggest (tactfully) that your instructor proofread his/her answer keys better.

-- Cheers, -- Mr. d.