The ancient monument of Stonehenge is one of the most spectacular sights of southern England. Why Stonehenge (A11) ... is still a mistery. There was a

The ancient monument of Stonehenge is one of the most spectacular sights of southern England. Why Stonehenge (A11) ... is still a mistery. There was atheory which stated that it (A12) ... a type of astronomical clock or calendar, by which the people of that time (A13) ... the seasons, hours of the day and the phases of the moon. However, up till now this theory (A14) ... . But there is no doubt that if the people who (A15) ... Stonehenge (A16) ... considerable engineering skills they (A17) ... to raise the enormous stones to make up the monument. Stonehenge is structurally unique among European prehistoric monuments and (A18) ... a large number of visitors every year. Quite recently the government (A19) ... the closure of the site because a number of stones (A20) ... to be unstable and now the remarkable monument can only be seen from a distance. A11. 1) has built 2) had built 3) was building 4) was built A12. 1) has been 2) had been 3) was 4) was being A13. 1) had calculated 2) were being calculated 3) had been calculated 4) were calculated A14. 1) hadn't proved 2) hadn't been proved 3) didn't prove 4) hasn't been proved A15. 1) were building 2) had been built 3) were built 4) have been building A16. 1) didn't possess 2) were not possessing 3) hadn't possessed 4) were not possessed A17. 1) weren't able 2) wouldn't be able 3) hadn't been able 4) wouldn't have been able A18. 1) is attracted 2) attracts 3) was attracting 4) has been attracted А19. 1) has announced 2) had announced 3) was announced 4) was announcing A20. 1) are considering 2) are considered 3) have considered 4) had been considering