Li Xin was called by the teacher to help a classmate. Her face wrinkled, but she still agreed, "Teacher, I will. Hongfei, if you have any questions, you can ask me. You haven't been here for a semester. I wonder if my grades have improved by a few places."

Although Qin Hongfei didn't have a good impression of her dog, she was eager to help Yun. To outsiders, she didn't come back for a semester, but in fact, she returned to the classroom after more than 20 years. Don't say... there may be many things she needs help with. So she

gladly accepted it, "Thank you."

This exchange was quite pleasant.

The first class was for homework. Qin Hongfei didn't have any homework, so she familiarized herself with the knowledge in the new textbook. From studying for a doctorate to studying in junior high school, it would be a bit hypocritical to say that she still remembered the textbook knowledge.

There was nothing left of the parents who had forgotten it long ago, but it was not to the point of forgetting everything. She could still remember it after reciting it.

Even if she couldn't remember the knowledge points, she could still understand it by herself.

Qin Hongfei familiarized herself with the textbooks she got, and immediately had an idea in her mind. Fortunately, the memory points were still there, and she made up for the missing ones and used them enough.

There would be no problem in promising the old lady 90 points.

As she was flipping through the pages, she saw an equation and paused. This question...

Li Xin had been looking at her. He knew that she had not studied it last semester and must have a lot of questions that needed help. Thinking of the teacher's instructions, she said with a little bit of arrogance, "What's wrong? What do you not understand? Do you need me to lend you my homework? Let me tell you, if the teacher hadn't asked me to lend it to you, I would definitely not lend it to you. Others want to borrow it but they can't. My grades are all excellent!" She said proudly.

Qin Hongfei really needed help. Li Xin was willing to help, so she asked without hesitation, "Well, there are some things I don't understand. How did you solve the equation in this question?"

Li Xin took a look. It was a chemistry equation.

The teacher had taught it last semester, but because he said that it would be taught in the second half of the semester, he didn't talk much about it.

Ribose is an essential substance for human life. Ribose is known to... After reading the questions, Li Xin suddenly had the confidence that she could get full marks on her test paper, just like the students who finished writing the test paper every time. "The teacher talked about this question before. I remember. Let me calculate it..."

Qin Hongfei was immediately interested and watched her convert.

Other students were bored and came over. With so many people, Li Xin had more face. She quickly solved the equation and the answer. She immediately received sighs and praises from other students. She was proud and showed it to Qin Hongfei, waiting for her admiring eyes and praise.

Qin Hongfei was also looking forward to it, but when she saw the final answer, she was speechless. She really shouldn't have placed such high hopes on her classmate who only walked the dog but didn't lead it. Seeing that other classmates were suspected of being misled, she said quietly out of friendliness, "Li Xin, your answer is wrong."

"How is that possible?" Li Xin retorted without thinking, "I remember what the teacher taught last semester, and you didn't come last semester. You didn't learn it at that time. How do you know it's wrong?"

She felt that she was right and did not accept any rebuttal.

Qin Hongfei said, "Because I know the answer to this question is, "C5H10O5." For