(1) is well-known that Antarctica is difficult to reach. (2) is well-known, Antarctica i——青夏教育精英家教网—

摘要： (1) is well-known that Antarctica is difficult to reach. (2) is well-known, Antarctica is difficult to reach. (3) is well-known is that Antarctica is difficult to reach. A. It B. Which C. What D. AS

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________is well-known is that Antarctica is difficult to reach.
A. What B. It C. As D. which