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 five

2. A number of important experiments have been carried out by them in this Laboratory

3. Central Africa was explored by Livingstone in the 19th century