Ответ:
When did electrification change every aspect of human life?
What did electrification change in the XIX century?
Who was battling Edison in those years?
Whom was Tesla battling in those years?
How will the voltage level be raised with inexpensive transformers?
What will the voltage level be raised easily with?
How many milliamperes of current does it take to cause heart fibrillation?
What role has DC maintained in modern life?
Where has DC maintained a crucial role?