The correct answer is C)19th.
The 19th amendment was the amendment which guaranteed all American women the right to vote. It passed by congress in 1919 on the 4th of June, and was finally ratified in 1920 on the 18th of August. The struggle for women's rights began in the middle of the 19th Century and included a number of marches, letters, lectures and civil riots and disobedience to finally get to achieve what many thought of as a radical change of the Constitution.
