Penicillin was discovered almost by accident. Returning from holiday, Fleming removed the tops from some old petri dishes and noticed that the bacteria he had grown were being killed by a mould - penicillin. He used the word antibiotic to describe penicillin.
The development of banking during the Commercial Revolution in western Europe was significant because it allowed for western Europe to expand their economy.
A should be correct. Kings were at the top of the feudal system while peasants/serfs were at the bottom. In between, there were knights and nobles/barrons and the land was split up between them.
He was impeached because he was lying under oath