Answer: B. spillover
Explanation:
A Spillover is used to refer to the effects of an Externality which is what happens when a market exchange leads to effects on a third party that was not party to a transaction between the contracting parties.
The activities that result from the transaction spillover to the third party and can be either negative or positive. A negative spillover would be countries in Africa getting harsher global warming effects due to companies in china polluting the atmosphere.