Good Riddles

Question: You see us everyday, but you never see us together. We appear everywhere but never are we together at the same place. Who are we?

Question: I can be seen, I can be not. Thanks to me, you'll fall in love. I mostly am sweet, but once I were sour. You can receive me, you can't just buy me. You only can send me, or simply share me. What Could I be?

Question: What is it you like to kill, but actually kills you?

Question: This is a fruit. You cross off the first letter it is a crime. Cross of the second letter its an animal. Cross off the next two letters it is a vowel. What is it?

Question: Jack is taking a tour through a museum's American Presidents exhibit. The person leading the tour tells him "We have a picture of each presidency. Currently Barack Obama is the 43rd person to hold the office." But Jack quickly realizes that there are 44 pictures on the wall. But while walking through the exhibit he realizes why this is.

Why is there one too many photos?