Which statement best describes how problem solving can lead to important inventions?

The stethoscope was invented by a French doctor who was embarrassed to put his head on women's chests to listen to their lungs.
In different areas, during the same time period, two versions of the thermometer were invented.
Typhus was less common in hospitals when patients were bathed and provided clean clothes and linens.
The tourniquet is used during amputations to cut the blood supply to the injured limb.