Short Riddles and Answers

Question: There was a man who was born before his father, killed his mother, and married his sister. Yet there was nothing wrong with what he had done.

Why?

Question: Nathan has math 4 times a week. If he has math 8:00 Monday, 9:20 on Tuesday, 10:40 on Wednesday, and 1:20 on Friday, when does Nathan have math on Thursday?

Question: Only one color, but not one size, Stuck at the bottom, yet easily flies, Present in sun, but not in rain, Doing no harm, and feeling no pain. What am I?

Question: I can be used to build castles,
but I crumble in your hands.
I can help a man see,
and am found all around the lands.

What am I?

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?