What work can one never finish?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?

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?

How can a man go eight days without sleep?

What Adam and Eve do not have but the rest of the people have?

Baseball bat and ball cost $100. If the bat cost $99 more than the ball, what is the cost of each?

If a shopkeeper can only place the weights on one side of the common balance. For example, if he has weights 1 and 3 then he can measure 1, 3 and 4 only. Now the question is how many minimum weights and names of the weights you will need to measure all weights from 1 to 1000? This is a fairly simple problem and very easy to prove also.

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

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?

What is so fragile that saying its name breaks it?