W is for........
War bonds. War bonds were things you could buy, like stamps. The money you used to buy a war bond goes to the war effort. At the end of the war you will get your money, that you used to buy a war bond, back.
X is For.........
X-ray. The x-ray wasn't invented during WWII, it was invented long before. Though it was there nobody used in war until WWII. The x-ray detected broken bones and other injures. The x-ray saved many lives of many soldiers.