EX1:

1)We studied a very hard lesson the day before yesterday
2)We have studied almost every lesson in this book so far.
3)We have never watched that television program.
4)We watched an interesting program on television last night .
5)My wife and I have traveled by air many times in the past.
6)My wife and I traveled to Mexico by air last summer
7)I have read that novel by Hemingway several times before.
8)I read that novel again during my last vacation .
9)I had a little trouble with my car last week.
10)However,I have had no trouble with my car since then.