After watching------TV,she played-----violin for an hour.

The answer is B
because in this situation,"TV" and "Violin" has confirmed to her.It means she knew which of the "TV" and the "Violin" ,so they need "the" ahead.
for example," I like "the" TV in that store"(I know which TV I m talking about,and I mean to it particularly)
otherwise,"I saw TV in that store"
( I dont mean any of TV particularly)
ps:"TV" means either the object or entertainments.it
depends on the sentence situation
hope this would helps!