Key to ex. 4 “Palaeontologists”:


1.     have unearthed

2.     have been digging

3.     found

4.     contained

5.     has been trying

6.     perished

7.     existed

8.     walked

9.     have been found

10.           has discovered

11.           has been

12.           were discovered

13.           has produced

14.           has allowed


(from Foley & Hall: Longman Advanced Learner’s Grammar)