You ............. travel to America without an entry visa.
a) can't b) mustn't c) had to
Thanks in advance.
See Changing the mood of a sentence (modals) - english-at-home.com for clarification.
However, in this example, I would choose "can't". They could have worded the sentence a little better by saying "You can't ENTER America without a visa", as opposed to "go to America". However, these days it's also true that you can't "go to" (ie travel to) America without a visa because airlines wouldn't actually allow you on the plane without the relevant documentation for entry.
thank you all.
Isn't mustn't more of a moral imperative? You mustn't say such things! You mustn't go to a dinner party without a hostess gift. You mustn't touch this cake before our guests come over.
While can't is an impossibility? You simply are unable to do it.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.