Mystery #11: General Science
Valentine Vexation

Elinor came into the room a bit late. As council president, she had been talking with the principal about some of the details.
Her friends were sitting around a table, blowing up balloons and snacking on the food some parents had brought. Soo was sipping fruit punch, Jada had a cupcake, Olivia was munching on carrot sticks and Cimone was eating a peanut butter sandwich. As each girl blew up a balloon, she used a marker to decorate it.
When they finished, Soo headed off to a corner to put up pink streamers while Cimone started to arrange flowers on the tabletops. Elinor, Jada, and Olivia gathered up some red, pink and white balloons and started to tape them onto the walls.
As she was getting ready to tape up one of the balloons, Elinor saw that a message had been written on it: "Elinor likes Gary."
"Who did this?" Elinor called out.
"That's for us to know and you to find out," Olivia said.
"I will find out," Elinor said, taking the balloon out into the hallway.
She soon returned and said, "Okay, Cimone, confess. I know you did it."
"How do you know," Jada asked?
Can you figure out how Elinor knows? Here's the answer:
"In the hallway, I unknotted the balloon and let the air out slowly, sniffing it as it came out," Elinor said. "I knew that the air in the balloon would smell like anything that was on the breath of the person who blew it up. The air smelled like peanut butter."
You can find the January mystery on Science, Naturally's website.