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

Solve the following series:
AZ, GT, MN, __, YB

People put me on the table and cut me but do not eat me. What am I?

You have four chains. Each chain has three links in it. Although it is difficult to cut the links, you wish to make a single loop with all 12 links. What is the fewest number of cuts you must make to accomplish this task?

You and your two friends are working in a multinational company. How can you three find out the average salary of you all without disclosing your own salary to the other two?

When it is alive we sing, when it is dead we clap our hands. What is it?

Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.

A woman named Maria was at the funeral of her mother. She met a nice young man that she had never seen before and after the service, they spent a bit of time together. Then she got busy and didn’t get his name or phone number before he left. She tried to find him, but no one knew who he was or how to contact him. A few weeks later, Maria’s older sister dies and the police suspect murder. Who killed the sister?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

The more of this there is, the less you see. What is it?