must versus should

[tahasozgen]

Hi there;
I have some problem about using must and should. I know their meaning, however in the questions below, I can not give correct answer. Here is the context of the should and must: http://blog.oxforddictionaries.com/2...-should-ought/


1-) You look very familiar. I ___ you before.

A) should have met
B) might meet
C) could meet
D) must have met
E) was supposed to met

My answer is A. Key depicts D. The link above says should :"to predict that something will probably happen or is expected to be the case, based on logic or a typical situation:"

2-) Jenny's engagement ring is enourmous! It __ a fortune.
A) must have cost
B) should have cost
C) was supposed to cost
D) would rather cost
E) used to cost

My answer is B. Key depicts A. Same logic with the question 1.

3-) Tim: While I was a student, I spent a year and a half studying Pygmy culture in the Central African Republic. I focused on unique aspects of their social structure and religion.

Simona: That __ absolutely fascinating.

A) ought to have been
B) would rather be
C) must have been
D) was supposed to be
E) will have to be

My answer is A. Key depicts C. Why ought to do not fit there? Since it is not a strong obligation, must shouldn't be there.

Thanks in advance.

[bhaisahab]

The answer key is right and you are wrong in each case. Is that what you were asking?

[Piscean]

'Must' can suggest not only obligation, but logical certainty:

John left here an hour ago. He must be home by now.
John left here an hour ago. He must have arrived home by now.

That's the situation in your sentences.

[emsr2d2]

You can replace "must have + past participle" in each case with "That's the only explanation" or "It's a certainty that ...".
You can replace "should have + past participle" in each case with "It would have been a good idea if ...". That wouldn't make sense in any of those situations.

You look very familiar. I must have met you before = You look very familiar. The only explanation for that is that I have met you before.
You studied hieroglyphics. That must have been fascinating = You studied hieroglyphics. For me, it's a certainty that that was fascinating.

[andrewg927]

ought to have been must be archaic since I have not seen or heard anyone use it.

Another example for must.

[Piscean]

ought to have been must be archaic since I have not seen or heard anyone use it.

It is not archaic in BrE, though it is not appropriate in any of those sentences.

[GoesStation]

ought to have been must be archaic since I have not seen or heard anyone use it.

It is not archaic in BrE, though it is not appropriate in any of those sentences.

Nor is it archaic in the American version. We're a lot more likely to use the synonymous should have been though.

[andrewg927]

Nor is it archaic in the American version. We're a lot more likely to use the synonymous should have been though.

LOL. I said it was an another example for must. That said, I would avoid using ought to have been altogether. It is lengthy and there are better ways to express the same idea.

[tahasozgen]

What is the meaning of ought to have been in British English and American English?

[GoesStation]

ought to have been must be archaic since I have not seen or heard anyone use it.

Another example for must.

LOL. I said it was an another example for must.

I finally understand what you were trying to say in the first quotation. I had had no idea what "Another example for must​" was supposed to mean.