they've finished
they're going to finish
they'll have finished
they finish
本题考查对将来完成时的判断与使用。“by＋时间”结构出现时，句子时态多用完成时，排除BD两项，分析语境，“本周三前完成”，为将来时态，故需使用将来完成时，C选项符合题意。句意：工人们说他们会在周三前刷完楼下房间的油漆。
