We plan to reach the North Pole in mid-July, and by then we for six weeks. A. ar
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We plan to reach the North Pole in mid-July, and by then we _______ for six weeks.
A. are walking B. have been walking
C. will be walking D. will have been walking
试题答案
D
句中by then短语表示一个将来的时间状语，所以谓语用将来完成时，因此选D。