"A hard one?" Zora said raising an eyebrow at this as she looked at Elisa with curiosity, "Sure, I am ready. What were you going to ask?" she asked questioningly.
This was indeed a bit more complicated than the others, Zora kind of knew the answer, but because she wasn't 100% sure, she had her doubts.
"Can I ask for a hint?" she asked. "I have an idea, sort of... it´s between Argon and Oxygen, I think, but I´m not sure which one it is?" she told Elisa.
Zora just looked at Elisa strangely when she gave her the hint. It took her a good minute to actually get what shells referred to. She had been thinking literal shells, not what it actually referred to.