Modal Verbs / модальные глаголы

Read the conversation and choose the correct words 

Chris:    This is a nice painting. Wow. Five thousand pounds! It [must / can /can't]  be by someone famous.

Betty:    Let me see ... er, it’s by Darren Hudson. I’ve never heard of him. 

Chris:    He [shouldn't/ *might/mustn't]  be one of those new Canadian artists.

Betty:    No, he [mustn’t / *can’t/may not]  be. All the artists in this exhibition are British.

Chris:    Oh. Look at this one. What do you think it is?

Betty:    I don’t know. It [*could / can/must]  be a person. Yes. I think it’s a woman.

Chris:    I’m not so sure. It [could / *might not/mustn't]  be a person. I think it looks more like a tree.

Betty:    No, it [mustn’t / *can’t/may not]  be that. Look, you can see the eyes, just there.

Chris:    Oh, yes, I hadn’t noticed them.

Betty:    There’s another one like it over there. [May it be / *Do you think/Mustn't be]  it’s by the same artist?

Chris:    It [*might / mustn't/couldn't]  be. Let’s have a look ... no, it’s got a different name on it.

Betty:    Well, I don’t like any of these paintings, anyway. Why don’t we go to the Bloomsbury Gallery? There [can / *should/may]  be lots of nice pictures there.

Chris:    Yes, but it’s already five o’clock. It  [*might not / could not/mustn't]  be open by the time we get there.

Betty:    I think it’s open until 6.30. I think we [must / *could/shouldn't]  get there in time.