How many sides does a circle have?

How many letters are in the alphabet?

If you say my name, I will no longer exist. What am I?

Can you spot what's wrong with the following sentence?

PETER WAS ANGRY AT
HIMSELF BECAUSE HE
ACCIDENTALLY LEFT THE
THE KEYS TO HIS CAR
AT HIS FRIEND'S HOUSE.

I came first on earth but second on the heaven.
I also came twice in a week but found just once in a year.
I stay away from months but you can find me in February.

What am I?

There are four 3-link chains. All you have to do is join them into a big 12-link chain. For joining two closed links, one of the links must be cut and placed onto the other link for closing.

How many minimum links will you have to cut to make the big chain?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

There are five vowels (a, e, i, o, u) in the English language.
Can you tell us a word that contains all these vowels?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

I don't get anymore wetter, no matter how much rain falls on me.