The manager entered the office and was happy to learn that four fifths of the tickets ___ .
问题描述：
The manager entered the office and was happy to learn that four fifths of the tickets ___ .
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答
had been sold out 根据所给语境,sell out(售出）之动作应该在was happy之前发生的,故应该使用过去完成时,且tickets与sell out之间为动宾关系,要用被动语态,综上所述,此空填had been sold out.