Present Perfect VS Present Perfect COntinuous

I'm tired. We _____________ for over an hour. Let's stop and rest for a while.

• have walked

• have been walking

The zoo isn't far from here. I ______________ there many times.

• have walked

• have been walking

I _____________ my friends at least a dozen letters since I left home.

• have been writing

• have written

Sally is writing a letter to her boyfriend. She ________________ it since she got home from class. It's going to be a long letter.

• have written

• have been writing

The telephone ______________ four times in the last hour, and each time it has been for my roommate.

• has been ringing

• has rung

My cellphone _________________ for almost 4 minutes.

• has been ringing

• has rung

She is 80 and she ________________ a book in her life.

• has never been reading

• has never read

The secretary is very tired. She ________________ all morning.

• has been typing

• has typed

Tom is reading a book. He started two hours ago and he is on page 53. He __________________ for two hours.

• has been reading

• has read

Hello! I _________________ the windows. So far I ______________ five of them and there are two more to do.

• have cleaned / have been cleaning

• have been cleaning / have cleaned