求翻译：她的脸上总是面带着微笑，显得非常和蔼可亲。她讲课时的样子严肃而认真又不失风趣幽默，仿佛是一位经验丰富的教授。李老师外表虽然非常平凡，但是她对学生的负责，对工作的认真，讲课的态度，却是不平凡的。是什么意思？

Her face always face with a smile, very amiable. Like when she lectures grave and serious, yet humorous, like an experienced professor. Li appearance very ordinary, but she is responsible for the students, work conscientiously, lectures attitude, but it is not trivial.

Her face with a smile on his face, was very amiable. She lectures look serious and carefully without losing the sense of humour, as if an experienced Professor. Mr Li looks very ordinary, but she is responsible for student to work seriously, lecturing attitude, but it is unusual.