Official Explanation:

Answer: D

(A) The subject one does not agree with the plural are estimated. Also, the correct idiom is estimated to be.

(B) The subject one does not agree with the plural are estimated.

(C) The singular has been excavated does not agree with the plural subject artefacts. The correct idiom is estimated to be.

(D) The correct answer.

(E) The singular has been excavated does not agree with the plural subject artefacts.
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My answer is (D). It took me 28 seconds.

The subject is singular (one), so the verb should be "is“ as opposed to "are". Eliminate (A) and (B).

In the relative clause, "that" refers to "the artefacts" (plural), so verb should be "have been" instead of "has been". Eliminate (C) and (E).

Now, we do not need to ponder over the idiomatic usage of "estimate". I think "Be estimated to be" is correct. I am pretty sure "be estimated at being" cannot be the right answer because, at least, "being" can be deleted. But how about "be estimated at more than 2000 years old"? I am not sure.

One of the artefacts that have been excavated from the recently discovered archaeological site are estimated at being more than 2000 years old.


(A) have been excavated from the recently discovered archaeological site are estimated at being
The main subject is 'one'. 'one' is singular. Note that 'that' refers to artefacts where the use of 'have' is correct. However, 'one' incorrectly refers to 'are' since 'one' is singular. SV error.

(B) have been excavated from the recently discovered archaeological site are estimated to be
Same reasoning as A.

(C) has been excavated from the recently discovered archaeological site is estimated at
'has' is incorrect when referring to plural 'artefacts'

(D) have been excavated from the recently discovered archaeological site is estimated to be
Correct use of 'have' when referring to artefacts. Correct use of 'one' with 'is'.

(E) has been excavated from the recently discovered archaeological site is estimated to be
'has' is incorrect when referring to plural 'artefacts'

One of the artefacts that have been excavated from the recently discovered archaeological site are estimated at being more than 2000 years old.


(A) have been excavated from the recently discovered archaeological site are estimated at being -> "estimated at being" is incorrect. Another issue, we have subject, one (singular subject).....are (plural verb)...Incorrect.

(B) have been excavated from the recently discovered archaeological site are estimated to be -> we have subject, one (singular subject).....are (plural verb)...Incorrect.

(C) has been excavated from the recently discovered archaeological site is estimated at -> One of "artefacts" (plural), so need "have been"....Incorrect to use "has been".

(D) have been excavated from the recently discovered archaeological site is estimated to be -> Both subject verb agreement issue is resolved. Let's keep it.

(E) has been excavated from the recently discovered archaeological site is estimated to be -> One of "artefacts" (plural), so need "have been"....Incorrect to use "has been".

So, I think D.

Ans D

One of the artefacts - The One here is singular so we need "is estimated". The usage of "are estimated" is incorrect.
Eliminate A and B

One of the artefacts
The word that come after one of the is plural. The "That" here refers to artefacts which is plural. We need 'have' and not singular 'has'.
Eliminate C and E for using 'has.

The correct answer is D.
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One of the artefacts that have been excavated from the recently discovered archaeological site are estimated at being more than 2000 years old.


(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

1. S-V: artefacts is plural shall be followed with have been
2. S-V: one of the artefacts is singular shall be followed with is
3. correct usage shall be estimated to be

IMo D
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One of the artefacts that have been excavated from the recently discovered archaeological site are estimated at being more than 2000 years old.


(A) have been excavated from the recently discovered archaeological site are estimated at being Incorrect

SV error - One of the artefacts singular, so is require

(B) have been excavated from the recently discovered archaeological site are estimated to be Incorrect

SV error - One of the artefacts singular, so is require

(C) has been excavated from the recently discovered archaeological site is estimated at Incorrect

artifacts plural, so has been wrong

(D) have been excavated from the recently discovered archaeological site is estimated to be Correct

(E) has been excavated from the recently discovered archaeological site is estimated to be Incorrect

artifacts plural, so has been wrong