Question

when a soil is classified using the international union of soil sciences system, its similarity to each of the 32 soil reference groups--defined by several criteria--______ evaluated, one group at a time, until a match is found. the comparisons are made in a specific order; thus, the criteria for kastanozems (soils with highly organic topsoil) are only applied if the soil doesnt match the criteria for planosols. which choice completes the text so that it conforms to the conventions of standard english? a are b was c have been d is

Explanation:

The subject of the sentence is "similarity", which is a singular noun. The verb should agree with the singular subject.

• Option A: "are" is plural, so it is incorrect.
• Option B: "was" is past - tense. The text is in present - tense (as seen from "is classified", "are made", etc.), so it is incorrect.
• Option C: "have been" is plural and also in a different tense form (present perfect) which doesn't match the overall present - tense context of the text, so it is incorrect.
• Option D: "is" is singular and in the present - tense, which matches the subject "similarity" and the overall tense of the text.

Answer:

D. is