Given a disfluent sentence, modify the sentence to it to its equivalent fluent form, preserving the meaning of the sentence.

Q: When did Goldbach or wait Landau propose his four conjectural problems?

A: When did Landau propose his four conjectural problems?
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Q: What castle currently concerts er uh houses the Centre for Ujazdow Art?

A: What castle currently houses the Centre for Ujazdow Art?
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Q: Who does, no actually, how many Africans were brought into the United States during the slave trade?

A:
How many Africans were brought into the United States during the slave trade?
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