Answer :
The answer is c because of where the comma is places in boys' and teacher's.
The correct answer is: The boys' comic books are on the teacher's desk.
The positioning of the apostrophe in both the subject (The boys' comic books), and the object (The teacher's desk) plays an important role in indicating property of plurals and singulars.
Taking account of the three boys and only one teacher present in this context:
The apostrophe after the s in boys' implies that more that one boy is owner of the comic books. In the case of one boy owning the comic books, the correct writing would be "boy's".
The apostrophe before the s in teacher's indicates the desk belongs to one single teacher. In the case of one teacher owning the desk, the correct writing would be "teachers'".