Final answer:
The NEC Article 820 requires a conductor not smaller than AWG 10 for grounding the shield of a coax cable; thus, the closest size from the provided options is AWG 12.
Step-by-step explanation:
According to the National Electrical Code (NEC) Article 820, when grounding the shield of a coax cable that is required to be grounded, a conductor not smaller than AWG 10 should be used. In the options provided, the size AWG that would fulfill the NEC requirements is AWG 12. The American Wire Gauge (AWG) system is a standardized wire gauge system used in the United States for the diameters of round, solid, nonferrous, electrically conducting wire. The larger the wire gauge number, the smaller the wire diameter. Wires are usually sold in terms of gauge rather than diameter, with household wiring commonly ranging from 10-gauge to 14-gauge.