It is + adj + that + S + should verb?

[vkhu]

There is an assignment that baffled me:
"It's strange that some of the survivors......... the crash."

My answer is survived but the key said it is supposed to be "should survive". I don't understand how can it be. This action happened in the past right? Why did they put "should survive" there?

[5jj]

'Survived' is acceptable. In formal British English, some speakers prefer to use 'should'.

[Raymott]

There is an assignment that baffled me:
"It's strange that some of the survivors......... the crash."

My answer is survived but the key said it is supposed to be "should survive". I don't understand how can it be. This action happened in the past right? Why did they put "should survive" there?

I agree. To me, "should have survived" sounds much better (if that's what you're implying)

On the other hand, it's logically impossible for the survivors not to have survived. So it shouldn't be that strange.