单项选择题
A.the circuit being worked on and the location of all switches and circuit breakers controlling it
B.first-aid techniques for treating electrical shock
C.cardiopulmonary resuscitation (CPR)
D.All of the above
单项选择题 An emergency generator, driven by an internal combustion engine, shall be tested under load for a minimum of 2 hours at least once every （）
单项选择题 Before any work on electrical or electronic equipment is performed, which of the following precautions should be carried out （）
单项选择题 Which of the following statements represents the FIRST precaution to be taken prior to working on any installed electrical component （）