It's Xiaoning who's speaking; Yan Fei heard her as soon as she arrived and purposely held up the book for her to see.
He got these French learning materials from America. Obviously, there isn't any Chinese text inside. The translations and everything are in English, which is what's frustrating Xiaohe and the others.
They thought Yan Fei was bragging when he said he'd learned English and Japanese, but turns out he wasn't kidding. He's studying French using English materials. They've got to accept it; that's how the gap arises.
Unexpectedly, Xiaoning is studying foreign languages, she's learned French, and even tried a few sentences with Yan Fei, then cheerfully said, "I was just thinking I can't practice my speaking, but now it's great. Shall we practice speaking together? Let me tell you something interesting. When He Qingzhi was at school..."
Yan Fei was worried he'd be studying behind closed doors with no practice, so he's happy to chat a bit with Xiaoning.
