第25题:[单选题]在紧急的情况下,应急马达发电机能向飞机提供()的电源。 A. 5KVA,115/200V,三相,400HZ B. 500KVA,115/200V,三相,400HZ C. 55KVA,115/200V,单相,400HZ D. 5KVA,220/380V,三相,400HZ 参考答案:A
第26题: [单项选择]During the Middle Ages, productivity of labor ______. A. was a primary concern of society B. was hampered by class relationships C. began to improve over levels reached by the Greeks D. was in a period of technical progress 参考答案:B 答案解析:可在第四句话“The social system of fixed... the Middle Ages (and in some areas much longer) itself hampered