We started to write to each other three years ago

16.We started to write to each other three years ago.
We have..
17.The last time I went to the museum was a year ago.
-> I last
18. I have never played golf before.
-> This is..
19.This is the first time I have seen a spacecraft.
-> I have..
20.John used to write home once a week when he was abroad.
-> John often..