zhè / dào / tí / ràng / quán / bān / tóng / xué / láo / xīn / kǔ / sī / zuì / hòu / hái / shì / méi / yǒu / zhǎo / dào / dá / àn

这道题让全班同学劳心苦思，最后还是没有找到答案。

This problem made the whole class think hard, but they still could not find the answer.