几万伏或几十万伏高压电能输送到负荷区后，必须经过不同的降压变压器将高电压降低为不同等级的电压，以满足各种负荷的需要。
参考答案：对
An analyst wants to get, crate a simple random sample of 500 stocks from all 10000 stocks traded on the New York Stock Exchange, the American Stock Exchange, and NASDAQ. Which of the following methods is least likely to generate a random sample（）
A. Listing all the stocks traded on all three exchanges in alphabetical order and selecting every. 20th stock.
B. Writing the name of each stock on a piece of paper, putting them in a hat, and drawing out 500 names, one at a time.
C. Using the 500 stocks in the S＆P 500.
有关招标代理机构的说法错误的是( )。
A．招标代理机构有评标的专业能力B．招标代理机构必须有营业场所C．上级主管部门可以制定招标代理机构D．招标代理机构应拥有“专家库”
