Riddles -Part 4

1. What has many rings, but no fingers?
2.  If you drop a Yellow hat into the Red Sea, What does it become?
3. What appears once a minute, twice in a moment, but not once in a thousand years?
4. What word begins with an E and ends with a E, but has only one letter?

1-A phone

2-Wet

3- The letter M

4-An envelope