Why does one person's mouth water at the mere mention of oysters .【C1】______ someone else's curls in disgust？ Puzzling【C2】______ the many reasons has left scientists feeling at times like blind men trying to【C3】______ an elephant. We are turned【C4】______ or off by the flavor, smell, texture and appearance of some food. Here, cultural biases come into【C5】______ .
We are born liking sweet tastes and disliking bitter ones.【C6】______ we learn other fondnesses and aversions. Psychologist Paul of the University of Pennsylvania assumed that we【C7】______ these things from our parents. But when he 【C8】______ the first survey on food preferences within families, he was【C9】______ to find he was wrong. Parents were proved to have no【C10】______ effect on their children's likes and dislikes or desire to try new foods.【C11】______ he concluded that cultural background is the single most powerful influence on our tastes because it 【C12】______ us to certain combinations of foods and flavors. Americans are familiar with salmon poached or broiled and【C13】______ with lemon, while the Japanese eat it raw and garnished with ginger.
But in a recent interview, Paul was quick to point to the 【C14】______ in his theory: "There's a lot of【C15】______ in tastes within nationalities." To be sure, not all Japanese like【C16】______ salmon, and many Americans have 【C17】______ their cultural bias against raw fish and now enjoy it. Individual food【C18】______ , Paul believes, "are【C19】______ .If you get sick on something once, you're not【C20】______ to eat it again."
【C1】

A. while
B. and
C. or
D. when