One of the artifacts that
have been excavated from the recently discovered archaeological site are estimated at being more than 2000 years old sentence correction
(A) have been excavated from the recently discovered archaeological site are estimated at being
(B) have been excavated from the recently discovered archaeological site are estimated to be
(C) has been excavated from the recently discovered archaeological site is estimated at
(D) have been excavated from the recently discovered archaeological site is estimated to be
(E) has been excavated from the recently discovered archaeological site is estimated to be
According to the grail, OA is D and the explanation states that plural subject "artifacts" has to agree with plural tense "have".
Based on my understanding "One" is the subject and is singular and hence option E correctly addresses the tenses.
Please clarify. Thanks in Advance