下列哪种动物的咽鼓管在鼻咽部膨大形成喉囊（咽鼓管囊）：（）
A.牛
B.羊
C.猪
D.鸡
E.马
参考答案：E
In a two - tailed hypothesis test, Jack Olson observes a t - statistic of -1.38 based on a sample of 20 observations where the population mean is zero. If you choose a 5 percent significance level, you should:（）
A. reject the null hypothesis and conclude that the population mean is significantly different from zero.
B. fail to reject the null hypothesis that the population mean is not significantly different from zero.
C. reject the null hypothesis and conclude that the population mean is not significantly different from zero.
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