No. 20

I used to think that the band of green I saw above a sunset was the green flash. I wish I had a picture to illustrate it, but anyway, it looked nothing like the green flash in this photo. I remember someone saying one that some people go their entire lives without seeing the green flash. Thanks to the internet, I'm not one of them.

Source -http://jef.raskincenter.org/pictures/green_flash.html