What does this simple rebus mean?

Why do you find that most of the buildings are deprived of the 13th floor?

How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?

Why is the Hole below a Lock?

Can you decipher the following common phrase?

T M C
A U O
H S M
W T E

A king sentenced a man to the death sentence for some crime he had committed. Known for his kindness, the king told the culprit that he had a choice to die in a way he decides.

The culprit was clever and said something that saved him from death. What method do you think he must have chosen for his death?

Two boys were admitted to a school. When the headmaster asks them about their parents, they tell him that they have same parents (father and mother). On further inquiry, it turns out that they both share the same date for their birthday.

"Are you twins," ask the headmaster.
"No," replies the boys.

Is it possible?

If I put in one canary per cage, I have one bird too many. If I put in two canaries per cage, I have one cage too many. How many cages and canaries do I have?

Find The Next Number in this series.
1, 2, 6, 42, 1806 ?