Test analysis: After the 1970s, the second industrial revolution was launched, electricity was widely used, and mankind entered the "electrical age", so C.

Comments: 1866 Siemens of Germany has successfully developed a generator. /kloc-in the 1970s, practical generators came out. At the same time, the motor was also made. The widespread use of electricity has changed the production and life of human beings, and thus human beings have entered the "electrical age". Electricity is an excellent and cheap new energy. Its wide application has promoted the rapid development of a series of emerging industries such as power industry and electrical appliance manufacturing. Subsequently, electric lights, trams, telephones, film projectors and so on appeared like mushrooms after rain, and human history entered the electrical age from age of steam.