Question

La profesora ____ los libros a los estudiantes.

Answer 1

The correct answer is B.
option A is for "Ellos" (they)
option C is for "yo" (I)
option D is for a third person but the conjugation works for "us." just try to translate the whole sentence: "The teacher gives us the books to the students." it does not make sense. 
However, if we use "B" the sentence is written properly. "La profesora les da los libros a los estudiantes" The teacher gives the books to the students.  

Answer 2

B. Les da is the answer :)