Explanation: In positive-logic circuits, the convention dictates that a higher voltage potential, or "high level," is used to represent a logic 1. This is the most common interpretation in digital electronics, where a specific voltage range is assigned to a logical "true" state. Conversely, in positive logic, a lower voltage potential, or "low level" (B), would represent a logic 0. If the circuit were designed using *negative* logic, then a low level would represent a logic 1. Options C and D, "positive-transition level" and "negative-transition level," refer to changes in voltage over time—a rising or falling edge, respectively—which are critical for timing and triggering events, but they do not define the static voltage level that represents a logic 1 or 0.