OG7 阅读 Q14

The second sentence of the third paragraph reads, "In economics, productivity — the amount of economic value created for a given unit of input, such as an hour of labor — is a crucial indicator of growth and wealth creation." In this context, the primary purpose of the appositive ("the amount of economic value . . . such as an hour of labor") is to define "productivity."
Choices A, B, and C are incorrect because in the context of the third paragraph, the appositive ("the amount of economic value . . . such as an hour of labor") is clearly provided to help explain the term "productivity," not to describe a process (choice A), highlight a dilemma (choice B), or clarify a claim (choice C).