重复抽样是指从总体中抽取一个元素后，把这个元素放回到总体中再抽取第二个元素，直到抽取n个元素为止。()

未分类题Why did the market fail to work its usual magic on human kidneys?A．The theory of demand and supply is not applicable here.B．Supply did not respond to high prices or meet fast growing demand.C．Supply of human kidneys depends on charity rather than market.D．Human kidneys are not such ordinary goods as shoes, clothes, etc.

未分类题According to Paragraph 4, which of the following is true about the debris?A．The white blood cells are ready to get rid of it all the time.B．It is the product of red blood cells during blood storage.C．It could help sports cheats avoid detection.D．It is fragments of cell membranes.

未分类题What would be the best title for the text?A．Blood Cell 'Debris' could Snare Sports CheatsB．A New Type of Blood DopingC．Several Measures Taken to Detect Blood DopersD．Antibodies are Created to Detect Blood Dopers

判断题对于连续变量，由于其变量值无法一一举例，所以更不能采用单项式分组，这种情况采用组距式分组。()

单项选择题在变容二极管电路中，中心频率fC为5MHz，调制信号频率为5kHz，最大频偏为2kHz。通过三倍频后，调频系数Mf为()。A、1.2B、2C、12D、15