Replace the question mark with the correct number in the below-given picture?

Why do we preferably have round manhole covers and not square ones?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

Why do people go to bed?

Can you count the number of blocks in the picture below?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

What is red and smells like blue paint?

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

Sherlock breaks into a crime scene. The victim is the owner who is slumped dead on a chair and have a bullet hole in his head. A gun lies on the floor and a cassette recorder is found on the table. On pressing the play button, Sherlock hears the message 'I have committed sins in my life and now I offer my soul to the great Lord' and followed a gunshot Sherlock smiles and informed the police that's its a murder.

Why did he think so?