【单选题】The case was crushed. It looks _________ the case was not strong enough to stand voyage.
【判断题】整流电路的功率因数为电网侧有功功率与视在功率之比。()
【判断题】通常同步电动机在过励状态下运行,以便从电网吸收超前电流,改善电网的功率因数。()
【简答题】若char ch='b',那么遇到下列语句会输出______。 switch(ch) {case'a':printf("it is a\n"); case'b':printf("it is b\n"); case'c':printf("it is c\n");break; case'd':printf("it is din");)