The correct answer is B: To cancel unwanted inductive reactance. The purpose of the series capacitor in a gamma match is to cancel unwanted inductive reactance. The capacitor's capacitive reactance cancels inductive reactance, making the impedance purely resistive and matched. A gamma match creates an inductive component due to the offset connection and the conductor's inductance. The series capacitor provides capacitive reactance that cancels this inductive reactance. At the design frequency, the capacitor's reactance equals the inductive reactance, they cancel, and the impedance becomes purely resistive (matched to the feed line). The capacitor is adjustable (variable capacitor) to tune the match. Without the capacitor, the gamma match would have a reactive component, causing high SWR.