Direction: Select the segment of the sentence that contains the grammatical…

Concept: Certain nouns that end in '-s' and look plural — politics, economics, mathematics, physics, news — are singular/uncountable when they name a field of study, a subject, or a general activity, and take a singular verb ('is'/'was'). The same word can become a genuine plural (with a plural verb) only when it refers to a set of countable individual things — e.g., a person's individual opinions or actions.

Application: In this sentence, 'politics' is used to name the general activity/profession as a whole ('politics ... is a dirty business to deal with'), not a set of separate opinions, so it must take the singular verb 'is'. The sentence instead uses the plural verb 'are' in 'are a dirty business', so segment (B) — 'are a dirty business' — carries the error.

• Contrast: if the sentence meant a person's individual political views, 'politics' could take a plural verb, e.g., 'His politics are quite extreme.' Here, the context — 'a dirty business to deal with' — is clearly about the general activity, confirming the singular sense.

• Segments (A) 'Sometimes politics' and (C) 'to deal with' are grammatically sound and need no change.

Answer: Segment (B) contains the error; the corrected sentence reads: 'Sometimes politics is a dirty business to deal with.'