a) Tu peux dire :
William Harvey come from England, Rene Laennec come from France, William Morton come from America and Alexander Fleming come from Scotland. They are all doctors.
b) Tu peux dire :
A doctor (William Harvey) had discover the blood circulation in 1578.
A doctor (Rene Laennec) had invent the first stethoscope in 1815.
A doctor (William Morton) had use anesthetics for the first time in 1846.
A doctor (Alexander Fleming) has discover penicilin (the first antibiotic) in 1928.
Voilan j'espère t'avoir un peu aidé! ^^