Tang Bohu sells paintings

On the banks of West Lake in Hangzhou, Ming Dynasty painter Tang Bohu hung an ink painting depicting a dog covered in black fur. On the right side of the painting, there is an explanation: This painting is a riddle painting, type one character. A buyer pays thirty taels of silver, but if they guess correctly, they won't take a penny and will receive this painting as a gift.

Drawing and hanging it attracted many tourists and passersby. People were guessing incessantly, but for a long time no one guessed correctly. At this moment, a scholar arrived and stood in front of the painting. Without saying a word, he took off the painting and left. People were very surprised to see this action. Tang Bohu hurriedly approached and asked, "Do you want to buy this painting?" The scholar shook his head. Did you guess this painting correctly? "The scholar nodded. Tang Bohu said, 'Please tell me the answer?' The scholar remained silent. Tang Bohu asked three more times, but the scholar still didn't answer. He took the painting and left on his own.

Tang Bohu looked at the back of the scholar and chuckled, "You guessed right! You guessed right!" After speaking, he walked away.

Reading while thinking: May I ask, children, what kind of characters are typed in this painting? Why did the scholar leave with the painting without saying a word? Did you guess?