The correct answer is D. He may not know child psychology.
A teacher should be keen in his work and should be enthusiastic and anxious to keep his knowledge fresh and update. He should have feelings of love and sympathy. His language should be understandable to students. All of these qualities are important for a teacher to have.
However, it is not necessary for a teacher to know child psychology. There are many other ways that a teacher can learn how to connect with students and help them learn. For example, a teacher can observe other teachers, read books about child development, and take courses on teaching.
Ultimately, the most important quality for a teacher is to be passionate about teaching and about helping students learn. If a teacher has this passion, he or she will be able to find ways to connect with students and help them learn, even if he or she does not know child psychology.