一个四棱锥的俯视图是______.
一个四棱锥的俯视图是中间有点的四边形.
故答案为:中间有点的四边形.
Which of the following statements about statistical concepts is FALSE()
A. A frequency is a tabular display of data summarized into a relatively small number of intervals.
B. An interval is a set of return values within which an observation not falls.
C. A parameter is an descriptive measure of a population characteristic.
以下肺上皮细胞通透性测定的数据处理,哪项是正确的()。
A.对双肺周边勾画感兴趣区,包括支气管等中心部分
B.肺清除拟合曲线为抛物线形
C.正常人肺上皮细胞通透性的放射性活度-时间曲线为双指数曲线
D.肺上皮损伤时,肺上皮细胞通透性的放射性活度-时间曲线为双指数曲线
E.测定肾脏的清除,可直接反映双肺肺上皮细胞的通透性