A man in a car saw a Golden Door, Silver Door and a Bronze Door. What door did he open first?

Solve the following series:
AZ, GT, MN, __, YB

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

Can you count the number of lines in the below picture?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

As shown in the image, the nine Dogs are square fenced. By constructing just two square fences can you make sure that two Dogs cannot meet each other without crossing the fence?

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

Can you find out who is the kidnapper in below Picture and why, Explain ?