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in the UK what is more preferable verb 'should' or 'ought to', or there is any differense in using them?

and how should I say:
I ought to follow him, oughtn't I?

Is that okay?
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In British English, "should" and "ought to" are (in the sense of obligation or recommendation) often interchangeable and equally acceptable. For example, "He should get more exercise" and "He ought to get more exercise" are both fine.

Two cases where I personally have a preference (for "should") are questions and negatives. For example, I would usually say "Should I do this?" not "Ought I to do this?", and "You shouldn't do that" not "You oughtn't to do that". As far as I can think, this is fairly typical of BrE speakers. The versions with "ought" aren't wrong though, and some speakers do use them.

In tag questions, such as your example, my preference doesn't seem so strong. I think I would theoretically prefer to say "I should follow him, shouldn't I?", but in practice I might easily begin with "I ought to" and then be obliged to complete with "oughtn't I?"

There may well be other specific situations where I have a preference for one or the other. It's very hard to immediately bring to mind every possible idiomatic usage.
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Such a perfect answer, thank you a lot!