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Riglos Posted 21 years ago
Grammar

have to/ should/ are supposed to

Hi again!

This sentence was one of the trickiest I encountered:

You _______ show your passport at the frontier if you want to get across.

a) have to b) are supposed to c) should d) are allowed to

Except for c), all others seems possible to me, though I find a) to be the most suitable, as "have to" stands for external obligation and, besides that's the correct one in the answer key.

Now, we use "be + supposed to" to talk about what people are expected to do because of an arrangement, a rule, or a duty:

E.g.: "You're supposed to start work at 8.00 every morning."

Since in the sentence in question we are also talking about a rule, why wouldn't b) be appropriate?

With regard to "should", isn't it also used to talk about obligation and duty? E.g.: "Guests should vacate their rooms by midday."

Why not choose c), then?

I'd really appreciate some clarification.

Thanks a lot!!

Mara.
  

Top answer

Suppose that the last part of the sentence were missing. You ____ show your passport at the frontier. In that case a) and b) both seem possible to me.

  • Suppose that the last part of the sentence were missing.
  • You ____ show your passport at the frontier.
  • In that case a) and b) both seem possible to me.
  • It is the "if you want to get across" that blocks the idea of expectation and stresses the idea of obligation.
  • "should" is a much weaker form of obligation, so it might be OK without the final "if" clause, but again only "have to" will work very well with the "if" clause.
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1 Answers
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Suppose that the last part of the sentence were missing.
You ____ show your passport at the frontier.

In that case a) and b) both seem possible to me.
It is the "if you want to get across" that blocks the idea of expectation and stresses the idea of obligation.

"should" is a much weaker form of obligation, so it might be OK without the final "if" clause,

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