happened to be no one in the building when the fire broke out.

________ happened to be no one in the building when the fire broke out. That's to say, ________ there was no one in the building when the fire broke out.

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A．It, it happened that

B．There, it happened that

C．This, it was happened that

D．That, that happened that

________ no one in the building when the fire broke out．So the building was almost destroyed．

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