Modal verb must Must be

Must be
Can be used to say that we are sure about something because it is logically necessary.
Употребляется для выражения предположения, которое говорящий считает вполне правдоподобным ( в чём он уверен). Must в этом случае переводится должно быть, а инфинитив – глаголом в настоящем времени.
The phone is ringing. It must be Ann.
( Звонит телефон. Должно быть, это Аня.)

Who can translate these sentences?
Mary and her friends go camping every weekend. That must be fun.
Jack never goes on excursion. He must think It’s boring.
The student must be in the classroom. They are writing a test.

Must have been
Is used with the Perfect Infinitive for deductions about the past.
Употребляется для выражения предположения, которое относится к прошлому.Must в таких случаях переводится должно быть, вероятно, а инфинитив – глаголом в прошедшем времени.
Mary and her friends went camping last weekend. That must have been fun.
(Мери и её друзья ходили в поход на прошлой неделе. Должно быть, это было весело.)

Who can translate these sentences?
Look! There is a crowd of people near the office. Something must have happened.
I waited for some time but nobody answered the phone call. Bob must have left already.
Jane is late. She must have missed her bus.

must have forgotten
1.Look! Here’s the letter John wrote yesterday. He to post it.
2.Jane is coughing all the time. She a cold.
3.He never visits such exhibitions. He it’s a waste of time.
4.The boy looks so excited. Something
5.All the students at the meeting. Important problems are being discussed.
6.She speaks English with a strong American accent. She in the USA for a long time.
7.Why is Peter so irritable this morning? He out of bed on the wrong side again.
8.She didn’t congratulate me on my birthday. She about it.
must have forgotten
must have caught
must think
must have happened.
must be
must have lived
must have got
must have forgotten

Translate from Russian into English
Майк, вероятно, перевёл этот текст.
Он должен быть сейчас в библиотеке.
Они, должно быть, забыли послать письмо.
Он, вероятно, сейчас дома.
Вы, должно быть, оставили книгу в школе .

Mike must have translated this text.
He must be in the library now.
They must have forgotten to send a letter.
He must be at home now.
You must have left the book at school.