What was the USS position during World War II?

The United States Navy grew rapidly during World War II from 1941–45, and played a central role in the war against Japan. It also assisted the British Royal Navy in the naval war against Germany and Italy

Its decreasing because of illnesses

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.