Thereweresomeseatsleftover_____eve

There were some seats left over _____every delegate had sat downA.whenB.untilC.thatD.where

参考答案：
A解析考查连词。when是引导时间状语从句的，表示“当……时候”。句意：当每个人都坐下的时候，还有椅子剩下。