Simple riddles with simple answers

Each morning I appear to lie at your feet. All day I will follow no matter how fast you run, yet I nearly perish in the midday sun.

You measure my life in hours and I serve you by expiring. I'm quick when I'm thin and slow when I'm fat. The wind is my enemy.

I am pronounced as a one letter alphabet. I am written with three letters. I am complete with just two letters. I am double. I am blue I am black I am brown I am gray I am yellow and I am green. I can read from both ends. I appear the same every way! What am I?

My life can be measured in hours. I serve by being devoured. Thin, I am quick. Fat, I am slow. Wind is my foe.

Born of water, I drown in water. A blood-thirsty beast you can barely see. What am I?

I am the biggest alphabet, as I contain the most water in the world. Who am I?

With thieves I consort, with the vilest, in short, I'm quite at ease in depravity; Yes all divines use me, And savants can't lose me, For I am the center of gravity.

Why is a river rich?

Never trust this fellow’s grin. His teeth are sharp and course, his blood’s as cold as icicles, and he’ll show no remorse! What is it?

A man is sitting in a pub feeling rather poor. He sees the man next to him pull a wad of £50 notes out of his wallet. He turns to the rich man and says to him, 'I have an amazing talent; I know almost every song that has ever existed.' The rich man laughs. The poor man says, 'I am willing to bet you all the money you have in your wallet that I can sing a genuine song with a lady's name of your choice in it.' The rich man laughs again and says, 'OK, how about my daughter's name, Joanna Armstrong-Miller?' The rich man goes home poor. The poor man goes home rich. What song did he sing?