Around the World in 80 Questions (Day 1): The quartzite found in the

Experts' Global Official Explanation:

Tenses + Modifiers + Idioms

A. Trap. This answer choice incorrectly uses the simple present tense verb “be metamorphosed” to refer to an event (the metamorphosis of the quartzite) that began in the past and continues into the present; please remember, the present perfect continuous tense (marked by has/have been) is the correct tense to refer to actions that started in past and continue into the present. Further, Option A incorrectly uses “believed to be metamorphosed since the deposition of the Triassic era” to refer to “Paleozoic mineral deposits” rather than “quartzite”, incorrectly implying that the deposits are believed to have metamorphosed since the deposition of the Triassic era; the intended meaning of the sentence is that the Santa Ana quartzite is considered one of the most pristine Paleozoic mineral deposits and believed to have been metamorphosed since the deposition of the Triassic era.

B. Correct. This answer choice correctly uses the present perfect continuous tense verb “have been metamorphosed” to refer to an event (the metamorphosis of the quartzite) that began in the past and continues in the present. Further, Option B correctly uses the independent clause construction “it is believed to have been metamorphosed since the deposition of the Triassic era”, conveying the intended meaning of the sentence- that the Santa Ana quartzite is considered one of the most pristine Paleozoic mineral deposits and believed to have been metamorphosed since the deposition of the Triassic era. Additionally, Option B correctly uses the singular verb “is” to refer to the singular noun “quartzite”.

C. Trap. This answer choice incorrectly uses the simple present tense verb “be metamorphosed”to refer to an event (the metamorphosis of the quartzite) that concluded in the past and continues into the present; please remember, the present perfect continuous tense (marked by has/have been) is the correct tense to refer to actions that started in the past and continue into the present.

D. This answer choice incorrectly uses “which was, it is believed, metamorphosed since the deposition of the Triassic era” to refer to “Paleozoic mineral deposits” rather than “quartzite”, incorrectly implying that the deposits are believed to have metamorphosed since the deposition of the Triassic era; the intended meaning of the sentence is that the Santa Ana quartzite is considered one of the most pristine Paleozoic mineral deposits and believed to have been metamorphosed since the deposition of the Triassic era.

E. Trap. This answer choice incorrectly uses the simple present tense verb “to be metamorphosed” to refer to an event (the metamorphosis of the quartzite) that began in the past and continues in the present; please remember, the present perfect continuous tense (marked by has/have been) is the correct tense to refer to actions that started in the past and continue into the present.Further, Option E incorrectly uses “whichare believed to be metamorphosed since the deposition of the Triassic era” to refer to “Paleozoic mineral deposits” rather than “quartzite”, incorrectly implying that the deposits are believed to have metamorphosed since the deposition of the Triassic era; the intended meaning of the sentence is that the Santa Ana quartzite is considered one of the most pristine Paleozoic mineral deposits and believed to have been metamorphosed since the deposition of the Triassic era. Additionally, Option E incorrectly uses the plural verb “are” to refer to the singular noun “quartzite”.

B is the best answer choice.