Final answer:
Outdoor receptacles must be labeled as weather-resistant and be GFCI protected to withstand exposure to moisture and environmental factors, as required by the National Electrical Code.
Step-by-step explanation:
The question asks which label must be on a receptacle that is located outside without a roof. The answer is that outdoor receptacles must be weather-resistant and also protected by a ground-fault circuit interrupter (GFCI). Receptacles in these locations are subject to moisture and environmental factors, therefore, they must be specifically designed to withstand these conditions. The National Electrical Code (NEC) in the United States dictates that outdoor receptacles must have a weather-resistant receptacle cover and be GFCI protected. It is worth noting that the actual wording on the label may vary, but it will typically indicate weather resistance.