Bunuel
The quartzite found in the Santa Ana Mountains is considered one of the most pristine Paleozoic mineral deposits,
believed to be metamorphosed since the deposition of the Triassic era.
(A) believed to be
(B) and it is believed to have been
(C) and that is believed to be
(D) which was, it is believed,
(E) which are believed to be
The sentence tells us two things about
Quartzite.
1. It is considered one of the most pristine Paleozoic mineral deposits.
2. It is believed to be metamorphosed since the deposition of the Triassic era.
The sentence connects two independent sentences by just using a comma. The correct way to connect to independent sentences is by using comma and FANBOYS or by using a semicolon. On the basis of this we can eliminate options A, D ,and E.
Now we are left with options B and C. Option B is correct because the sentence uses
"since" which in this sentence is used to indicate time. Whenever since is used as an indicator of time. It talks about an action that started in the past and is continuing in the present.
For ex. I have lived in London since 2005.
And option B correctly shows an action that started in the past and is continuing in the present and also connects two independent clauses correctly. "
and it is believed to
have been metamorphosed since the deposition of the Triassic era."
Therefore option B is the correct answer.