How can you make number one disappear by adding something to it?

Which of the below owl is odd one out?

Spelt forwards I’m what you do every day, spelled backwards I’m something you hate. What am I?

Name the three-letter word that can complete the below words:

A) L O _ _ _ E
B) E D U _ _ _ E
C) _ _ _ E R
D) _ _ _ T L E

You need to pick one entry from pot A and one from pot B to have a perfect match. Can you do it?

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

What has a ring but no finger?

A girl was sitting in her hotel room when she heard a knock on the door. She opened the door and found that a man was standing outside.
The man said, "Oh! I am really sorry, I thought this was my room."
He then walked through the corridor to the elevator. The girl did not know the man. She closed her door and called security asking them to apprehend the man.
What made her suspicious of that man? He might have been genuinely mistaken.

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

I taste better than I can smell. Who am I?