might have/could have

[azz]

a. Twenty people could have been killed in that attack. Fortunately the we acted rapidly and nobody was killed.
b. Twenty people might have been killed in that attack. Fortunately the we acted rapidly and nobody was killed.

c. Twenty people could have been killed in that attack. We don't yet know how many people were killed.
d. Twenty people might have been killed in that attack. We don't yet know how many people were killed.

Which of the above sentences are grammatically correct?

The idea is that the first sentences are ambiguous.

They might mean:
1. It was possible that twenty people would be killed. That didn't happen.
and
2. It is possible that twenty people were killed.

 

[jutfrank]

Apart from the fact that you've included a stray word and haven't included a comma in the second sentences of a and b, they're all grammatical.

What's your question exactly? If you want to imply that nobody was killed, use could.

 

[azz]

Thank you jutfrank.

Yes, the question. If there's a difference between 'might' and 'could'? It seemed that (b) is not incorrect, but (a) is better. Nobody was killed in the first pair of sentences.

Many thanks.

 

[jutfrank]

Are you asking whether there's a general difference between might and could? Or are you asking specifically about these sentences?

It seems to me that your thinking is approaching the right lines. I think you've sensed that the modal might is better when the idea is that there is a real possibility (people have really died) and could is better when the possibility is only theoretical (nobody actually died). So sentences a and d are the examples you should focus on.

 

[Tdol]

I was taught the following way:

may have died = have possibly died
might have died = didn't die

Some people still use it, but the distinction seems the be getting rarer.