Short Riddles and Answers

Question: Alone I am 24th, with a friend I am 20. Another friend and I am unclean.What am I?

Question: I am a digit, but two of the ten.
Two of me make a promise.

What am I?

Question: What do these things all have in common: Laughter, living well, and a good offense?

Question: Which eight-letter word still remains a word after removing each letter from it?

Question: One night a man and woman got on th boat. The man and woman got off. Who were left.