Could/might have been

Can I use 'for the last hour' in the first sentences of the conversation?

Anonymous Jack: What might/could Alex have been doing for an hour? James: He may/might have been cleaning his room. Is the conversation correct with 'could/ might+have+been'?

Yes. I prefer it with the words I've added in red.

CJ

Anonymous Can I use 'for the last hour' in the first sentences of the conversation?

Yes. That would be fine.

CJ

Anonymous'For an hour/for the last hour/for the past hour' mean the same, right?

No! "for an hour" is during any hour, even an hour last month or last year.
"for the last hour" or "for the past hour" is the hour preceding the time the words are said.
"for the last hour" can also mean the last hour of an activity of several hours, and this activity mig

But the conversation above 'might/could have been' is connected to present, right? So, 'the last hour in the conversation' means 'from an hour ago to present time (at the time of speaking), right?

AnonymousBut the conversation above 'might/could have been' is connected to present, right? So, 'the last hour in the conversation' means 'from an hour ago to present time (at the time of speaking), right?

Yes, as long as there was nothing previously in the conversation that specifically mentions an activity of several hours in the past. This condition seems