How do i answer this question in spanish "quién es la maestra? "

The translation for that sentence is: Who is the teacher? So you answer it with a name. Since it is a teacher you must use Mr., Ms., or Mrs. in this case, maestra is feminine so you'll need to use Señora(Mrs.) or Señorita(Ms.).

The answer is b.a, c, and d are not correct

What do u mean are u asking a question