Contrary to popular belief, video games aren t just for

Contrary to popular belief, video games aren‘t just for killing an idle Thursday evening,
in fact, a variety of recent studies have begun to demonstrate their teaching potential.
A. video games aren‘t just for killing an idle Thursday evening, in fact, a variety
of recent studies have begun to demonstrate
B. video games aren‘t just to kill an idle Thursday evening, but a variety of
recent studies, in fact, have begun to demonstrate
C. video games aren‘t just for killing an idle Thursday evening; in fact, a variety
of recent studies has begun to demonstrate
D. video games aren‘t just for killing an idle Thursday evening; in fact, a
variety of recent studies have begun to demonstrate
E. video games aren‘t just for killing an idle Thursday evening, and a variety of
recent studies have begun in demonstration of

Should 'a variety of' have verb for the object after 'of'? I chose C which was not OA!
Please explain!
Thanks!!