如图，树、红旗、人在同一直线上，已知人的影子为AB，树的影子为CD，确定光源的位置并画出旗杆的影子．

将下列句子改为被动语态
(1)I sent a letter to you last month.
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(2) Do we use it for cooking?
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(3) Where did you build the bridge?
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(4) Mother tells me a story every day.
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(5) Can he finish his homework on time?
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下列各命题中，其逆命题是真命题的是（   ）