The correct answer is C: A figure-eight broadside to the axis of the array. Two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase create a figure-eight pattern broadside to the axis of the array. The pattern has lobes perpendicular to the line between antennas. When two antennas are fed in phase with 1/2-wavelength spacing, they reinforce in the broadside direction (perpendicular to the line between them) and cancel along the axis. This creates a figure-eight pattern with the lobes broadside to the array. The in-phase feeding and 1/2-wavelength spacing are key to this pattern. This is different from 180-degree out-of-phase feeding, which creates an end-fire pattern along the axis.