计算样本容量，如果总体比例的值不知道可以用样本比例来代替，或者取总体比例值为0.5，使得π（1-π）达到最大。（）
参考答案：对
Please ________ this form, giving your name, age and address. [ ]
A. fill with
B. fill in
C. full with
D. full in
In the following essay,each blank has four choices．Choose the best answer and writedown on the answer sheet． Communicating via E—mail is by far the most common Internet activity．You can (71) with anyone in the world who has an Internet address or E—mail (72) with a systemconnection to the Intemet．All you need is (73) the Internet and an E—mail program．Two ofthe most widely used E．mail programs are Microsoft’s (74) and Netscape’S Navigator．Atypical E．mail message has three basic (75) ：header，message，and signature·
A．packets B．elements C．frames D．cells
