Simple

Continuous

Perfect

am

is + Vз(Ved)

are

I am given a task every lesson.

(day by day, every day, weekly, usually, often, never, sometimes, at first…, then…)

am

is being+ Vз(Ved)

are

The house is being built now.

(now, at the present moment..)

have (has)+ Vз(Ved)

The book has already been sold.

(today, this week, this month, this year, never, ever, already, lately, since…)

was (were)+ Vз(Ved)

The boys were examined by the doctor.

(yesterday, two days ago, last year, in1980, every day, often, always, at first, then…)

was (were) being+ Vз(Ved)

At that moment the article was being written.

(at 7 o'clock, at that moment, when…, while…, from…till, all day long)

had been+ Vз(Ved)

The book had been sold by the end of the week.

(by 5 o'clock, by the 15^th of May, by the end of the week, before)

will be+Vз(Ved)

The letter will be written tomorrow.

(tomorrow, next week, next year, every day, often, always, at first, then)

will have been+Vз(Ved)

The work will have been done by 3 o'clock.

(by 7 o'clock, by the 15^th of May, by the end of the week, before)