can't or mustn't

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TryToExploit

Member
Polish
Hello, just a quick question because I think there is a wrong answer in my book :)

Choose the sentence with the same meaning.
I'm sure she isn't feeling sick now.
a) She can't be feeling sick now.
b) She mustn't be feeling sick now.

Thanks in advance.
 
  • reno33

    Senior Member
    English - USA
    I don't think either one applies. Neither a nor b has the same meaning as [ I'm sure she isn't feeling sick now. ]
     

    TryToExploit

    Member
    Polish
    I think we are not supposed to change a negative sentence into a positive one.
    The answer in the book is "mustn't be feeling sick" o_O

    My answer was: "can't be feeling sick" and was resulted by this:
    1585758022169.png


    Do these sentences have the same meaning?
    She can't be serious.
    I'm sure she's not serious.
     

    Packard

    Senior Member
    USA, English
    We use "must" to describe something that is unavoidable or required. We use "should" describe something that is suggested.

    I should go to work today, but I don't feel like it.
    (suggested)

    I must go to work; my company depends upon me
    . (required)

    She must not feel sick, we need her at work. (We wish that she is not sick.)
    She cannot be sick for all this time. (It is not possible for her to be sick for that length of time.)
     

    lingobingo

    Senior Member
    English - England
    My (UK) take on it is:

    I'm sure she isn't feeling sick now =
    a) She can't be feeling sick now, can she? :tick:
    a) Surely she can't still be feeling sick? :tick:
    b) She mustn't be feeling sick now :cross: (implies it’s not allowed!)
     
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