When economists say that people act as rational decision makers, they mean that:
a. they gather all relevant information before making their purchases. b. once a pattern of behavior has been established, people tend to become set in their ways. c. people respond in predictable ways to changes in costs and benefits. d. people rarely make errors when they are permitted to make transactions.

c. people respond in predictable ways to changes in costs and benefits.

Explanation:

Hello! For the branches of the economy, people act in one way or another (not always rational) based on different “reasons.” Some of the reasons why people act like that are measured, such as costs and benefits. In general, economists know the most predictable reactions a citizen will have.  

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answer; (d) one tectonic plate plunges beneath another; (most common,convergent boundaries)

the invasive species was introduced due to commercial purpouses, as there was a demand for fur clothes and hence, a business opportunity connected to this product. actually, it was when the nutrias scaped, causing harm to the us ecosystems when they acquired the status of invasive species. in this case they have caused an environmental problem, but it could have affected also economic interests or even human health.