Explanation

　　1.The correct answer is C

　　Choice (C) is correct. It avoids the error of the original by following both parts of the “both … and” construction with the pronoun “his” (“In both his … and his … ”)

　　2.The correct answer is C

　　Choice (C) is correct. It avoids the error of the original by using the idiomatic “known as” instead of the awkward and unidiomatic “known to be.”

　　3.The correct answer is D

　　Choice (D) is correct. It avoids the error of the original by removing the unnecessary pronoun “it.”

　　4.The correct answer is B

　　This sentence illustrates a comma splice, the incorrect use of a comma to connect two complete sentences. Choice (B) correctly uses a semicolon to coordinate two independent clauses and form a compound sentence (while at the same time keeping verb tenses parallel). The correct sentence reads: One of the most common types of mistakes that inexperienced physicians make is misreading symptoms; another one that occurs about as frequently is recommending inappropriate treatment.

　　5.The correct answer is C

　　Choice (C) is correct. It avoids the verb tense error of the original. The past tense verb “remained” is not consistent with the present perfect tense verb “have made” and should be changed to the present tense verb “remain.”