Good Riddles

Question: A boy was born before his father, killed his mother, and married his sister. How is this possible?

Question: A bat and a baseball together cost $1.10. The bat costs a dollar more than the ball. How much does the baseball cost?

Question: A farmer has 10 cows, all but six die. How many are left?

Question: What flag has five circles in it?

Question: While you were folding a letter I got you.
Usually you will do whatever it takes to avoid me,
but now you can't help but find me.

What am I?