Why did rice become an important crop after the arrival of African slaves

What does this quotation from the introduction of thedeclaration of independence do?

Which statement below accurately describes the carrying capacity of any ecosystem? a. it is not affected by any abiotic or biotic resources. b. it does not affect the species of an ecosystem. c. it is completely dependent upon the food supply. d. it is affected by both abiotic and biotic resources

The occurs when someone offers an unnecessary reward beforehand in an obvious effort to control behavior.