In this task, you need to replace a letter in the sentence with another given letter.

Q: Sentence: 'a small train is on the tracks by a house'. Replace the letter 'l' with 'x' in the sentence.

A: a smaxx train is on the tracks by a house
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Q: Sentence: 'a man is standing on a snowboard, atop a mountain'. Replace the letter 'd' with 'u' in the sentence.

A: a man is stanuing on a snowboaru, atop a mountain
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Q: Sentence: 'a building has a clock on the top of it'. Replace the letter 'l' with 'x' in the sentence.

A:
a buixding has a cxock on the top of it
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