Find out the contrasting sentences in Bai Juyi's poem "The Charcoal Seller" and talk about their respective functions.

It is half a piece of red yarn and one foot of silk, tied directly to the cow's head and filled with charcoal.

Through comparison, it profoundly writes about the poor life and difficult situation of the charcoal seller, and reveals the exploitation and oppression of the people by the rulers. .

The charcoal seller earns money from selling charcoal to buy clothes and food. The old man is "dressed neatly", and the "foot of snow" that comes at night and the "icy ruts" on the road are used as foils, making people feel even more "poor" about the old man. And all this reflects the burning fire of the old man's hope: the weather is cold and charcoal is expensive, so he can buy more clothes and food.

Next, "the cow is trapped and the man is hungry" and "two graceful riders" reflect the disparity in the situation of workers and rulers; "a cart of charcoal, more than a thousand catties" and "half a piece of red yarn "Zhang Ling" reflects the cruelty of "Gongshi" plunder. As far as the whole poem is concerned, the blazing fire of hope in the front is precisely to contrast the sadness and pain of hope in the end.