单选题 At present, it is not possible to confirm or to refute the suggestion that there is a causal relationship between the amount of fat we eat and the______of heart attacks
【正确答案】 A
【答案解析】解析：句意：目前，既不能肯定也不能否定脂肪的摄入量和心脏病的发病率之间是否存在着因果关系。 “incidence”可能性， “impetus”动力、推动力， “rupture”破裂、裂开， “emergence”出现。因此，答案为A。