某研究者，为了验证氯霉素对伤寒的疗效，在408例伤寒病人中进行对，隋实验，其中251例用氯霉素治疗，其余157例不用。结果使用组251人中死亡20人，死亡率7.07%，未用组157人中死亡36人，病死率22.8%，已有结论被亲自证实。
在临床医学研究中，对受试者应该做到的是（）
In recent years, railroads have been combining with each other, merging into super systems, causing heightened concerns about monopoly. As recently as 1995, the top four railroads accounted for under 70 percent of the total ton-miles moved by rails. Next year, after a series of mergers are completed, just four railroads will control well over 90 percent of all the freight moved by major rail carriers.
Supporters of the new super systems argued that these mergers will allow for substantial cost reductions and better coordinated service. Any threat of monopoly, they argue, is removed by fierce competition from trucks. But many shippers complain that for heavy bulk commodities travelling long distances, such as coal, chemicals, and grain, trucking is too costly and the railroads therefore have them by the throat.
The vast consolidation within the rail industry means that only one rail company serves most shippers. Railroads typically charge such "captive" s
A. cost reduction is based on competition
B. services call for cross-trade coordination
C. outside competitors will continue to exist
D. shippers will have the railway by the throat
Once the 12 Girls Band became popular, similar groups predictably starting popping up. Musicat and Beautiful Youth 18 were formed last year. Both feature now-familiar formulas of attractive young women playing different instruments in songs that combine modem music with classic Chinese tunes. Yet they add to the mix by throwing in song, dance and even acrobatics. In an interview, noted music critic Jin Zhaojun said the gift band phenomenon was not new to China, as similar acts appeared in the 1980s.
However, the undying rule is that to be successful, bands have to have a novel look. "The 12 Girls Band was the first group to give big live shows and showy creativity in how they present their performances. The Beijing Red Poppy Ladies Percussion group, formed in 1999, has made a name for itself because they are the only band that exclusively plays drams and percussion instruments. Bands that don’t have ’a thing’ are sure to die fast," Jin said.A. They are the only band that exclusively plays drams and percussion instruments.
B. They don’t make use of any instrument.
C. All of them play the same kind of instrument.
D. They play different instruments in songs that combine modem music with classic Chinese tunes.
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