JT-C型机车信号的双套热备是指由主机内双套主机板、（）、双路接收线圈共同组成的双套热备系统。
参考答案：双路电源
Research _______ that over 90 percent of high school students are dissatisfied with their test scores.
A．indicates
B．introduces
C．dictates
D．determines
除氧器给水箱内安装再沸腾管的作用是什么？
