Tammy Ate Raw Oysters for the First Time And, Four

Tammy ate raw oysters for the first time and, four hours later, became extremely sick to her stomach. Now, the smell of oysters makes her stomach queasy. What is the CS?

A) the smell of the oysters
B) a bacterium or other toxin that was definitely present in the oysters
C) a bacterium or other toxin that may or may not have been in the oysters
D) stomach queasiness