A mad scientist was studying the behavior of frogs. He put a frog on a flat surface, shouted "jump", and the frog jumped up in the air. He reached for his notebook and wrote down, "Frogs can jump."

Then the scientist removed one of the frog's legs and shouted "jump". The frog jumped and the scientist wrote down, "Frogs can jump with three legs."

Then the scientist removed another leg and shouted "jump". The frog jumped and the scientist noted, "Frogs can jump with two legs."

Then he removed a third leg and shouted "jump". With difficulty, the frog jumped and the scientist wrote, "Frogs can jump with one leg."

Then he removed the frog's one remaining leg and shouted "jump". The frog didn't move.

The scientist repeated the command. The frog did nothing.

The scientist concluded in his notebook, "Frogs, when deprived of all legs, become deaf."