Hello!

Um... you're gonna have to help me out a bit here.

I'm not sure what your question is.

The correct answer for the question is C.

The reason it's not A is because milk contains other sugars aside from lactose 

(for example other types of oligosaccharides)

and also I agree with your teacher, lactose can also be cut into glucose and galactose.

Let me know if you have any other questions. thanks! :D