The Enlightenment and Revolutions - Modern Science 

The 20th century ranges from January 1, 1901 to December 31, 2000
During those years their was many great inventions that were discovered. As for me these Three advancements seem most important. 
1. The radio
2. Antibiotics
3. The airplane

Alexander Fleming in 1928 discovered penicillin from Penicillium notatum mold, sadly he did not receive a noble prize until 1945 when he was 64 years old. He didn't realize how important his discovery was, for a decade later he focus more on how the Penicillin could cure wounds and surface infections. As he left it for his fellow Noble prize winners 

Howard Florey and Ernst Chain to demonstrate in 1940 that Penicillin was capable of curing numerous bacterial disease's. Alexander went to school at the age of 13, studying to be a physician
he got a scholarship to st. Mary's  hospital medical school in Paddington, London. After completing his studies he decided to stay working at the hospital and found a new drug called salvarsan to cure syphilis. After it was synthesized he maintained a small profit from administrating salvarsan to wealthy patients suffering from syphilis. Having these drugs and the several others that came to light resulted in a longer-lifespan to soldiers and the nation. These drugs have helped find a cure for the past problems like small pox, typhoid to gonorrhea and syphilis and many others. 

In 1895 Guglielmo Marconi (goo-lee-air / Mar-cone-ie) invented what he called "the wireless telegraph." He used radio waves to transmit Morse code  and the instrument he used became known as the radio. The radio has allowed people to be heard over hundreds and even thousands of miles away. It has allowed ships

to communicate out at sea, It has formed Europe's most famous broadcasting company or BBC to play classical music, plays and various programs in witch Marconi was involved in. The radio was the second family life during world war 2, it held on my a tread in the fifties when it was soon replaced by television. Now a days it seems to only be useful in cars to keep drivers from falling asleep. Today it has a very vital existence compared to the microwave, Cellphone's, and the computer. The radio had been "upgraded" so the speak, that it now comes on cellphones and computers, They have websites that play music for you and record the broadcast for you to listen later on. In a way the radio still exist, but in new forms of life. 

George Cayley invented the first glider that flew with men aboard. Although the brilliant idea flew men and were definitely better than the hot air balloon, the glider was still difficult to control and couldn't travel long distances.  The Wright brothers, Orville and Wilbur, Invented the first airplane with the start of interest in flying. After they tinkered with gliders Cayley invented, they researched airplanes from books. Over time after many attempts and improvements they invented a kite with 

two wings in 1899. Creating models and noticing errors they were able to correct them and create more sophisticated machines that could accurately tell them were things needed to be. Then they invented one that could be piloted while in the air by adding flaps to the rear end of the plane. They became the first team to fly a airplane in December 1903. Airplanes have come to the point to help with crop dusting, fighting forest fires to overnight deliveries or even chasing hurricanes. Airplanes simply make the world shrink by a few hours in the air. 

Reason for my ranking

Although all of the advancements each bring something great, I think that Antibiotics would come first because it made a huge impact to solider's and in a family's life giving a loved one longer to live. I rank the radio second because the radio allowed many people to communicate worldwide, broadcasting music and communicating to someone out at sea. I would rank the airplane last, Although it was very effective it still needed work as well as any other invention, They worked there best and did it with interest in flying. Giving kudos to the Wright brothers for inventing transportation, crop dusting and fighting wildfires.