阅读下列材料:
“有心杀贼,无力回天,死得其所,快哉快哉!”
请回答:
(1)上述材料出自何人之口?
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(2)材料中的“贼”指谁?
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(3)此人为什么会发出“无力回天”的感叹?
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(4)上述材料表现了他怎样的精神?
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