The British scientific community was surprised when a five-millimeter

Question

The British scientific community was surprised when a five-millimeter-long lagoon spire snail,  thought to have been extinct in Britain for 2,000 years , was found in a pond in Chichester Harbor.

A. thought to have been extinct in Britain for 2,000 years
B. which was thought to be extinct in Britain from 2,000 years ago
C. which, for 2,000 years, was thought as extinct in Britain
D. thought extinct in Britain 2,000 years ago
E. thought as extinct in Britain 2,000 years ago

prabsahi · Answer

A looks correct

Note ..for 2000 years demands a perfect tense since it's not a definite time period .

Also thought as..is wrong usage.. it means more like saying though as equivalent to..

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mitrakaushi · Answer

The question can be best understood by understanding the meaning.

1. (No errors) 
2. 'from 2000 years' ago is awkward.
3. It was thought as extinct conveys that the snail = extinct. But snail is in the state of being extinct, snail and extinct are not the same. As can only be used before a noun when it conveys that the preceding noun is adopting a role.
4. It means that the snail was considered extinct 2000 years ago but not now
5. Same problem as 3.

sudarshan22 · Answer

+1 for   A  .

A.  thought to have been  extinct in Britain for 2,000 years -->   Correct , idiom usage   'thought to ..'   
B.  which  was thought to be extinct in Britain  from 2,000 years ago 
C.  which , for 2,000 years,  was thought as  extinct in Britain
D.  thought  extinct in Britain 2,000 years ago
E.  thought as  extinct in Britain 2,000 years ago

Hence,   A  .

Abhishek009 · Answer

Nothing wrong with the original sentence, cut the fluff, it seems perfect -

The British scientific community was surprised when a five-millimeter-long lagoon spire snail , thought to have been extinct in Britain for 2,000 years,  was found in a pond in Chichester Harbor.

Errors in other options marked in red, correct Answer must be (A)

aragonn · Answer

Official Explanation: 
For the intended meaning - something that went on for two thousand years and just got over, use of present perfect continuous tense is truly called for.

A. Correct. Uses the appropriate tense and so conveys the intended meaning.

B. "to be" is incorrect tense. "from 2,000 years ago" is incorrect. "which was" is unnecessary.

C. "thought as extinct" is ungrammatical. Placement of "for 2,000 years" is not too apt.

D. "thought extinct" is incomplete. "thought extinct...2,000 years ago" changes the meaning.

E. "thought as extinct" is ungrammatical. "thought...2,000 years ago" changes the meaning.

patto · Answer

Can anyone explain why B is incorrect? thanks

DmitryFarber · Answer

Mahmud6  We can't ever say "thought to had been." In this case, "to have" is an infinitive, so it can't change at all. We'd say all these:

I believe them to have been an couple. 
(I think that the two were a couple before now, but not any longer. I think they have been a couple at some point in the past.)
 I believed them to have been a couple. 
(It might be simpler to say "I thought they had been a couple," but if I use the fancy initial construction here, "to have" is needed.)
 Until yesterday, I had believed them to have been a couple. 
That last one is a mouthful, but it would mean that before yesterday, I thought they had been a couple, but now I don't think that.

DmitryFarber · Answer

patto  B is wrong because we can't say something was "extinct from 2,000 years ago." We think that it has been extinct for 2,000 years, or that it went extinct 2,000 years ago, but "from 2,000 years ago" doesn't have a sensible meaning in this context. We could say something like "we found a clay pot from 2,000 years ago," but that's about it.

varunbawa · Answer

I got the errors in other but can you explain, that why we are using  have  in option 1. If you can provide some details it would be really helpful.

DmitryFarber · Answer

All of these are examples of the "perfect infinitive." You use it to refer to an action that precedes the other verb in the sentence, but since it's an infinitive, you don't change the tense of "have." Often, there's an easier way to say the same thing (e.g. "I believe that they were once a couple," "I believed that they had been a couple," "Until yesterday, I had believed that they were a couple"), but you may see this form occasionally.

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The British scientific community was surprised when a five-millimeter

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The British scientific community was surprised when a five-millimeter

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