What occurs twice in a week, once in a year but never in a day?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

There are forty elephants and they have forty-fore heads. How can this be possible?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

Four men were in a boat on the lake. The boat turns over, and all four men sink to the bottom of the lake, yet not a single man got wet! Why?

Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

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?

Can you solve below mathematical equation?

2^1234 - 2^1233

This is a picture puzzle. You have to guess the name of the movie that can be related to the picture.

Which digit occurred maximum times between the number 1 and 1000?