The Three Doors (Medium)

Question: There are three doors: First door~ all kinds of snake will strike you once you've entered this door. Second door~ about thousands of skillful assassins are waiting in this door. Once you've entered, they will attack you to death until there are no bones left. 3rd door~ a desert, you will be die any minutes. Because there's no water (exhaustion) and from extreme the heat of the sun. Which door would you choose? Which door you think that is safe to enter???

Question: People see through me, but none pass through without killing me. I can be anywhere, and can be seen double or single. What am I?

Question: During what month do people sleep the least?

Question: When is 99 more than 100?

Question: What can be broken but never forgotten?

Question: What gets broken without being held?