Can you replace the question mark with a number?

Little Johnny watched the science teacher start the experiment with the worms. Four worms were placed into four separate jars.
The first worm was put into a jar of alcohol
The second worm was put into a jar of cigarette smoke.
The third worm was put into a jar of sperm.
The fourth worm was put into a jar of soil.

After one day, these were the results:
The first worm in alcohol - dead.
Second worm in cigarette smoke - dead.
Third worm in sperm - dead.
Fourth worm in soil - alive.

So the Science teacher asked the class - "What can you learn from this experiment."

Little Johnny quickly raised his hand and said - "As long as you drink, smoke and have sex, you won't have worms."