The whole poem is:
Half an acre of square pond opened, and the sky was overcast.
How can the canal be so clear? Because there is inexhaustible living water for it.
This sentence mainly uses rhetorical devices such as rhetorical questions and metaphors.
First of all, the poem asks itself and answers itself, which embodies the rhetorical device of asking questions; Secondly, the meaning in the poem is "Why is it so clear?" ? Because the rivers keep gathering. Zhu, a great scholar, realized some truth in praising reading. The carefree, clear and lively perception in his mind is reflected in ponds and clouds. Why is his mind so clear? Because there is always new knowledge in the book, like running water, which is constantly supplementing him!