После окончания высшего учебного заведения начинающий врач-стоматолог Дарья П. стала искать работу по специальности. Она обратилась в фирму «Стоматолог и я»,

1. Are my friends building their own house now?
    What are my friends building now?
    My friends are building their own house now, aren't they?
    Are my friends building their own or my house now?
2. Has he known him for a long time?
    Whom has he known for a long time?
    He has known him for a long time, hasn't he?
    Has he known him or her for a long time?
3. Does the office usually close at  at 7 o'clock in the evening?
    When does the office usually close?
    The office usually closes at 7 o'clock in the evening, doesn't it?
     Does the office usually close at 7 o'clock or 8 in the evening?
4. Will the chief engineer be visiting the construction site in the suburds of the town from      2 o'clock till 4 o'clock tomorrow?
     When will the chief engineer be visiting the construction site in the suburds of the town?
    The chief engineer will be visiting the construction site in the suburds of the town from 2 o'clock till 4 o'clock tomorrow, willn't he?
     Will the chief engineer be visiting the construction site in the suburds of the town from      2 o'clock till 4 o'clock tomorrow or after tomorrow?