Explanation
Correct answer: B.
Choice B is the best answer because it most accurately describes how the underlined portion functions in the text as a whole. The underlined portion is a parenthetical phrase directly following the word “microfilm,” and it describes film containing small (“scaled-down”) images; the placement and focus of the portion indicate that it is serving to define the term “microfilm.”
Why the other choices are wrong
Choice A
Choice A is incorrect. Although the text is about accessing the writings of a famous historical figure (Douglass), the underlined portion doesn’t give information about Douglass or any other person. Instead, it explains what microfilms are.
Choice C
Choice C is incorrect because the text never describes any kind of debate or disagreement; it simply describes a change in how researchers can access historical documents, with the underlined portion defining an important term.
Choice D
Choice D is incorrect because the text never makes any mention of a particular finding, unexpected or otherwise; it simply describes a change in how researchers do some of their work, with the underlined portion defining an important term.