◎ 题干
—Has Jack finished his homework yet? I am waiting for him.
—I've no idea. But he _____ on it the whole afternoon.
[     ]
A. is working
B. works
C. was working
D. worked
◎ 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“—Has Jack finished his homework yet? I am waiting for him. —I've no idea. But he _____ on it the whole afternoon.[ ]A. is working B. worksC. was workingD…”主要考查了你对  【过去进行时】  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。