what the differences between "it must be" and "it must have been"

[shinji002]

Dear Mr Answer

what the differences between "it must be" and "it must have been"

[beascarpetta]

it's simply a matter of tense I'd say

"It must be terribly difficult to get along with her" refers to the present

whereas

"It must have been difficult to last as long as she did" refers to past events

hope this helps.

[riverkid]

Dear Mr Answer

what are the differences between "it must be" and "it must have been"

It is a matter of tense as B says. As to meaning, the first describes a situation that, in the speaker's mind, holds true right now.

She must be at work.

The second describes what the speaker thinks about a certain situation that has now finished.

[10PM at night]
She must have been at work today.

[shinji002]

got it , thank you~