This sentence combines two ways of forming comparisons. The “more” in unnecessary. The corrected sentence reads: "Shaking himself out of his reverie, the author reflected that he had rarely been wearier."

"Most" is a superlative that is only used when at least three items are being compared. Here, only two items are being compared ("simple tools" and "electronic devices"). Therefore, "more" is the proper word choice, not "most." "Most effectively" is therefore the part of this sentence that contains an error.

When two items or people are being compared, the appropriate word for the comparison is "better," not "best." Therefore, "best" contains the error; there were two applicants, so "better" should have been used, not "best," which is used to compare three or more items or people.

When comparing more than two things, the superlative version of an adjective should be used. "Better" would be used to compare two experiments, but in this sentence, the word "best" should be used. So, "better" is the part of the sentence that contains the error.

The double use of "very" is an empty superlative; it serves no purpose in formal written American English, which is what the SAT is testing.

In this sentence, there is an illogical comparison between Maria’s birthday party (a thing) and Susie (a person). Assuming that the comparison should be between two birthday parties, the corrected sentence reads: "Maria had a gigantic bouncy castle at her birthday party, making it significantly more popular than Susie’s party."

In the above sentence, two subjects are being compared: the knight and the samurai. When a sentence compares only two subjects, it is appropriate to use the comparative form ("more") rather than the superlative form ("most") of adjectives.

This sentence uses a superlative (“most”) when it is only comparing between two things. The comparative “more” would be better. The corrected sentence reads, "I used to find information about public transportation on the printed schedules, but I have discovered that the online ones are the most helpful."

"Less than" should be changed to "fewer than." When deciding whether to use "less" or "fewer" in relation to a give noun, if you can count that noun or it has a plural ("people," "glasses of water," etc.) "fewer than" is grammatically correct, and if you can't count it or it has no plural ("time," "money," "water," measurements) "less than" is grammatically correct. As an example, you would say "less water," but "fewer buckets of water."

The phrase "the more expensive of the three" contains this sentence's error. Three types of sweaters are being compared: acrylic sweaters, wool sweaters, and cashmere sweaters. The comparative adjective "more" is used; this is incorrect because comparative adjectives are only used for comparing two things, as in the sentence, "I like vanilla ice cream more than chocolate-covered strawberries." When comparing three or more things, a superlative adjective should be used. In this case, that means that "more" should be changed to "most" to correct the sentence's error.