a present simple

*: “36% of the world's population is still affected by poor hygiene.”

b present perfect

*: “Infection and disease haven't been eliminated entirely in our hospitals yet, but they have been significantly reduced.”

c past continuous

*: “up to half of Lister's patients who had survived surgery were being killed by infections spread by germs.”

d will future

*: “medical organisations will be challenged in the future by new infections and diseases;”

e present continuous

*: “Although hygiene in developing countries is being improved all the time,”

f past simple

*: “Louis Pasteur and Joseph Lister's revolutionary ideas about using sterile instruments in clean hospitals were adopted in the 19th century.”

g past perfect

*: “they had been taught about the importance of cleanliness by their religious leaders.”