What always comes into a house through the keyhole?

Which alphabet letter is a question?

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?

In the image given, you can find several triangles. Can you count them all?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

What do you see in the given picture?

You see me once in June, twice in November, and not at all in May. What am I?

If eleven plus two equals one, what does nine plus five equal?

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

My location can be determined by the below rebus.
So where am i ?