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 have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

You see a mathematical expression in the picture. Can you think of a movie that this expression refers to?

Can you Find and name the hidden bird in the picture below ?

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

What does this rebus mean?

O
N
C
E
TIME

By moving just one matchstick, you need to make the below statement true. Can you do it?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?