Many models predict that as climates warm, North American tree popula… | Verbal SAT Question

Which choice best describes the overall structure of the text?

Many models predict that as climates warm, North American tree populations will expand northward into newly suitable habitats. However, forest surveys show that many species, such as the chestnut oak (Quercus montana) and the Engelmann spruce (Picea engelmannii), are exhibiting migration lag—that is, they are failing to establish northern populations as predicted. Research suggests that this lag is linked to reduced diversity of essential fungal partners at the northern edges of the trees’ habitats, making it difficult for these trees to successfully expand northward.

It presents a scientific prediction, describes evidence that contradicts that prediction, and then offers an explanation for the contradiction.

It introduces a scientific model, presents several predictions made using data generated by the model, and then provides further support for one prediction over the others.

It summarizes recent research findings, identifies a gap in current understanding, and then suggests future research to address that gap.

It describes an environmental problem, discusses several attempted solutions, and then proposes a new solution.