Found this question in a book:
The Oldest repertory theater still existing ______ founded in 1680.
a) the Comedie-Francaise in Paris, it was
b) is the Comedie-Francaise in Paris, was
c) which is the Comedie-Francaise in Paris,
d) the Comedie-Francaise in Paris, was
The right answer seems to be B from simple punctuation perspective (if there is no comma - we definitely need "is"); however, the relative clause concerns me.
As I understand, we can reduce nonrestrictive relative clause only if it has some form of "to be", but "was" should be removed as well then, or can I leave it?
Another option could be that "was founded in 1680" is a restrictive clause, but it's the only one "the Comedie-Francaise" theater historically.
My last option is just a parallel clause:
The Oldest repertory theater still existing is the Comedie-Francaise in Paris. The Oldest repertory theater still existing was founded in 1680.
Any suggestions?