What type of conductor must be covered for safety purposes?

The requirement for safety coverage primarily pertains to live conductors operating at 50 volts or more. These conductors can pose a significant shock hazard, and insulating or covering them minimizes the risk of accidental contact. The use of appropriate protective coverings can prevent electrical injuries from exposure to live parts, ensuring safety for anyone who might work near or alongside these conductors.

In this context, service conductors, while also critical, do not encompass all safety considerations that live conductors present, especially since any live conductor is potential risk given their voltage. Non-serious conductors typically refer to those that are not carrying current under normal operating conditions, and therefore, they do not necessitate safety coverings like their live counterparts. Grounding conductors are intended to carry fault current safely to the earth and do not require the same type of coverage since their function is primarily safety-oriented and not prone to accidental contact in the same manner.

Thus, live conductors operating at 50 volts or more are specifically designated for coverage to mitigate the risk of electric shock, making this the correct answer.