Today’s SAT question of the day is an identifying sentence errors question about starfish and sea urchins.

The starfish and sea urchins manage to swim clear of the error in this sentence, but the seas are not so lucky.

The second half of the sentence reads, “[they] inhabit all seas except that of the polar regions.” Inhabit is conjugated correctly. The sentence tells us there is more than one polar region, so we have to infer that there is more than one sea. “That of ,” however, says that there is only one sea. Those of would be the correct option, because we would say “Hey, look at those seas,” not, “Hey, look at that seas.”

Check all pronouns, adjectives, and verbs to make sure they agree in tense, number, etc., and trust your ear – it will almost always be right when it hears something wrong. (Here, those is a pronoun acting as an adjective…but don’t let that trouble you.)