Based on the clue '1 of the 3 things we mutually pledge to each other...', what is the answer?

Based on the clue '1 of the 3 naturally occurring magnetic elements', what is the answer? What is associated with: 1 of the 3 planets you wont be able to see with the naked eye in 1989? Based on the clue '1 of the 3 sections of the small intestine', what is the answer? What is associated with: 1 of the 3 singers on the 1993 no 1 hit all for love from the film the three musketeers? What is associated with: 1 of the 3 things which according to john fremonts 1856 gop campaign should be free? Based on the clue '1 of the 3 types of muscle it has a built in contr...', what is the answer? Based on the clue '1 of the 3 us presidents to run on a third party t...', what is the answer? Based on the clue '1 of the 3 villains to have their name in a film t...', what is the answer?