◎ 题干
There are still many problems ______ before we are ready for a long stay on the Moon.
A.solvingB.solved
C.being solvedD.to be solved
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“There are still many problems ______ before we are ready for a long stay on the Moon.A.solvingB.solvedC.being solvedD.to be solved…”主要考查了你对  【现在分词的被动式】【现在分词】【不定式的被动式】【过去分词】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。