Choose the correct options to complete the text.

In 1918, just as the First World War was ending, there was a major outbreak of flu. Today, this virus (1...) as 'Spanish flu'. Five hundred million people across the world (2...) with the virus between 1918 and 1920. Many soldiers, who (3...) for their battle injuries in hospitals, caught the disease. Historians believe that, by the end of 1920, 100 million people (4...) by the virus. Flu can still be a dangerous illness and research (5...) at the moment to try to develop stronger and more effective vaccinations against it. New treatments (6...) and in the future, scientists hope that a cure (7...)?

1 A is known B is knowing
2 A are infected B were infected
3 A being treated B were being treated
4 A had been killed B had killed
5 A is being done B is doing
6 A be tested B have been tested
7 A will be discovered B will discover