I believe all of the answers are true. 1) If the background is lit more that the subject it will appear just as a shadow, or you will have a very unflattering picture. 2) when photographing wildlife the photographer will often blur the edges to draw the viewers focus to the main image. 3) true the eye will automatically look at what is in focus rather than straining to see what is not. 4) true
It means representing semi structured data in human-readable ext form, mostly composed of symbols and lists and extensively used in the Lisp programming language.