What is the best way to change this sentence from passive voice to active voice?

The course was being failed by half the students near the end of the school year.


A.
Half the students were failing the course near the end of the school year.
B.
The course, near the end of the school year, was by half the students being failed.
C.
Near the end of the school year, the course was being failed by half the students.
D.
Failing the course near the end of the school year were half the students.