An old man knew that he was studying late. In front of a poem, I don't know what the last sentence is until I am old.

1, the last sentence is that black hair doesn't know how to study hard. This poem comes from the Tang Dynasty poet Yan Zhenqing's "Persuade to Learn".

2. The original text of the whole poem is as follows: It is the night when men study. Teenagers only know how to play, but don't know how to study hard. When they are old, they regret why they didn't know how to study hard when they were young.

3. In the vernacular, crowing from midnight to night is the best time for boys to study. When I was a teenager, I only knew how to play and didn't know how to study hard. When I was old, I regretted why I didn't know how to study hard when I was young.