Riddle

What can be seen, but cannot be touched, and when put in a barrel, will make the barrel lighter?

Choose an answer

A.A shadow
B.A hole
C.Reflection
D.A beam of light
Hint: It's a 4-word phrase with 12 letters, starting with "A".

Answer

A beam of light

Why this is the answer

Light is visible yet intangible, and adding it doesn't add physical weight to anything.

This riddle is filed under How, What, Why Riddles and rated Medium.