21) Electric currents above approximately 6 milliamperes are considered: a. not harmful b. primary currents c. harmful d. secondary currents e. "b" and "c" above 22) When operating gas cylinders, the primary valve should be opened: a. all the way on an acetylene cylinder b. one turn on an oxygen cylinder c. one turn or less on an acetylene cylinder d. all the way on an oxygen cylinder to backseat the valve e. "c" and "d" above
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