Переделайте следующие предложения в Passive Voice
1. They were playing tennis from four till five
2. They have carried out a number of important experiments in this Laboratory
3. Livingstone explored Central Africa in the 19th century

1. Tennis was being played by them from four till five2. A number of important experiments have been carried out by them in this Laboratory3. Central Africa was explored by Livingstone in the 19th century