Question

biologists have yet to agree on a single concept of what defines a species. thus, numerous competing species concepts are used within the field, a dilemma known as the species problem. the cohesion species concept, described in 1985 by templeton, defines species in accordance with phenotypic cohesion. the genetic species concept, delineated by baker and bradley in 2006, organizes species according to genetic similarity. which choice completes the text with the most logical transition? a for instance, b therefore, c in fact, d on the other hand,

Explanation:

The text first presents the overall dilemma in species - definition. Then it gives an example of how Baker and Bradley organized species according to genetic similarity. "For instance" is used to introduce an example. "Therefore" implies a conclusion, "in fact" emphasizes a fact, and "on the other hand" shows a contrast. Here, an example is being introduced, so "for instance" is the most appropriate.

Answer:

A. for instance,