Explanation

　　1.The correct answer is E

　　The error in this sentence occurs at (D), where there is an improper idiom. The idiom is “best known as,” not “best known to be.”

　　2.The correct answer is E

　　There is no error in this sentence.

　　3.The correct answer is B

　　The error in this sentence occurs at B. The relative pronoun “that” may not be used to refer to people (“individuals”) and should be replaced with the relative pronoun “who.”

　　4.The correct answer is D

　　The error in this sentence occurs at (D). When a comparison is introduced by the adverb "more," as in "more effectively," the second part of the comparison must be introduced by the conjunction "than" rather than "and not."

　　The other options contain no errors. In (A), the plural verb "have discovered" agrees with the plural subject "students." In (B), the plural pronoun "they" correctly refers to the plural noun "students." In (C), the preposition "through" appropriately expresses the means by which issues are addressed.

　　The sentence may be corrected as follows: The students have discovered that they can address issues more effectively through letter-writing campaigns than through public demonstrations.

　　5.The correct answer is D

　　The error in this sentence occurs at (D), where there is an inappropriate pronoun. The singular pronoun “that” is needed to refer to the singular noun “manner.”

　　6.The correct answer is D

　　The error in this sentence occurs at (D). A pronoun must agree in number (singular or plural) with the noun to which it refers. Here, the plural pronoun "their" incorrectly refers to the singular noun "committee."

　　The other options contain no errors. In (A), the preposition "After" appropriately introduces a phrase that indicates when the committee made its decision. In (B), "to postpone" is the verb form needed to complete the description of the committee's decision. In (C), the prepositional phrase "of the resolution" appropriately specifies the subject of the postponed discussion.

　　The sentence may be corrected as follows: After hours of futile debate, the committee has decided to postpone further discussion of the resolution until its next meeting.