How many triangles are there on the puzzle below?

Replace the question mark with the correct number.

John was visiting his friend Jacob. He found out that his friend's wife had just killed a burglar in self-defense.
John asks Jacob about what happened and he told that "His wife was watching television when suddenly the bell rang. She thought that it is her husband Jacob but she found the burglar who attacked her instantly and she got so frightened that she killed the burglar immediately with the knife.
John asked the police to arrest his friend's wife. Why?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

What is wrong in the below Picture?

What happened when the wheel was invented?

You are given four results as below:
1111 = F
2222 = E
3333 = T
Then, can you find out how to code 4444?

Find the missing letter in the last circle logically in the given below picture.

Decode below rebus
D
N
A
T
S , D

What brings you down but never up?