Why can't I use "couldn't" here?

[roseriver1012]

It's said that there are plenty of hotels in the small seaside city. So there_________ be any difficulty for you to find somewhere to stay at this moment if you want to have a trip there.

A. couldn't B. mustn't C. shouldn't D. needn't
The answer is "shouldn't". Why can't I choose A? I know "shouldn't" is right here. But I can't tell why "couldn't" is not right in case my students ask me. So please help me! Thanks!

 

[bhaisahab]

It's said that there are plenty of hotels in the small seaside city. So there_________ be any difficulty for you to find somewhere to stay at this moment if you want to have a trip there.

A. couldn't B. mustn't C. shouldn't D. needn't
The answer is "shouldn't". Why can't I choose A? I know "shouldn't" is right here. But I can't tell why "couldn't" is not right in case my students ask me. So please help me! Thanks!

If you use "couldn't", you are implying that it is impossible that there would be no rooms available.

 

[roseriver1012]

If you use "couldn't", you are implying that it is impossible that there would be no rooms available.

Do you mean that "couldn't" here is too strong? But isn't it weaker than "can't"? If "can't" is used here, I would think it means it is impossible that... Then does "couldn't" here send the same message as "can't"?

By the way, just out of curiosity, the time in my region (China) now is pm 15:34, shouldn't it be a sleep time for Brits?

 

[bhaisahab]

Do you mean that "couldn't" here is too strong? But isn't it weaker than "can't"? If "can't" is used here, I would think it means it is impossible that... Then does "couldn't" here send the same message as "can't"?

By the way, just out of curiosity, the time in my region (China) now is pm 15:34, shouldn't it be a sleep time for Brits?

Yes, "couldn't" sends the same message as "can't" in this context. In France (where I am) it's morning, 09:52 and in the UK it's 08:52.