Fill the spaces in the following sentences by using for or since

IV. Fill the spaces in the following sentences by using “for” or “since”:

1- They´ve been working _________ five or six hours.

2- Nobody has come to see us _________ we bought this small house.

3- She has been a doctor_________ 1998.

4- Nobody has seen her _________ then.

5- They have all been ill _________ the last week.

6- They hasn´t spoken to us _________ we were at school.

7- He bought the car in 1999 and has driven it _________ then.

8- Peter went to the library. He has studied there _________ a long time.

9- It has been very foggy _________ early morning.

10- I´ve worked with you _________ nine years