Scientists gathered three musicians together and asked them to name the greatest invention of the 20th century. The guitarist said the “wah-wah pedal” was the greatest invention.
After that, they asked the drummer and he said the “bass pedal” was the greatest invention.
Then finally, when asking the bass player, he said the “Stanley thermos” was the greatest invention.
Confused, they asked him how he figured that, and he said:
“Hot or cold how does it know, HOW DOES IT KNOW!?!?!?!”