1.The correct answer is A

　　The error in this sentence occurs at (A), where there is inappropriate word choice. In this context, “Except for” doesn't make sense. Instead, “Without” is needed.

　　2.The correct answer is A

　　The error in this sentence occurs at (A), where there is awkward and wordy phrasing. The awkward “Long been” should simply be “Long” (“Long isolated...”).

　　3.The correct answer is B

　　The error in this sentence occurs at (B), where there is subject-verb disagreement. The singular verb “is” is needed to agree with the singular noun “the number.”

　　4.The correct answer is C

　　The error in this sentence occurs at C. The plural verb “have” does not agree with the singular subject “writer” and should be replaced with the singular verb “has.”

　　5.The correct answer is C

　　The error in this sentence occurs at (C), where there is subject-verb disagreement. The plural verb “make” does not agree with its singular subject, “An abundant supply.”