Fun Riddles

Question: 4 people fall out of a boat and only 3 get their hair wet.

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

Question: I am a big threat to humanity,
but you wouldn't get rid of me even if you could.

What am I?

Question: In Michigan you cannot take a picture of a man in a green hat.

Why?

Question: There are two boys at an international math contest in December 2013; one is British and one is American. They both write their names, the date, and their answers on the paper. The only problem is that they both have the same name and the papers cannot be told apart.

What is the date?