Explanation: Split tuning, also known as "double hump," describes the frequency response of two resonant circuits that are *overcoupled*. When two tuned circuits, such as those in an intermediate frequency (IF) transformer, are tuned to the same frequency but have excessive (more than critical) coupling between them, their combined frequency response changes. Instead of a single, sharp peak at the resonant frequency, the response "splits" into two distinct peaks, one slightly above and one slightly below the original resonant frequency, with a dip in the middle. This characteristic shape, with two peaks, is visually referred to as a "double hump." Option C, "critical coupling," is incorrect because critical coupling is the point of optimum coupling, where the bandwidth is maximized without the response splitting into two humps. It's the point just *before* overcoupling occurs.