In synchronous digital design with positive clocking, the flip-flop responds (captures input and changes state) only when the clock signal is at its active high condition (e.g., during a high level or a rising edge, depending on design).

Introduction / Context:Flip-flops are the building blocks of synchronous sequential circuits. Their state changes in response to a clock signal, which defines when data is sampled and propagated. Positive clocking means the active portion of the clock is the high condition (often specifically the rising edge in edge-triggered devices). Understanding the active clock condition is crucial for correct timing design.

Given Data / Assumptions:

• The term “positive clocking” is used to denote an active-high clocking convention.
• We are considering standard level- or edge-sensitive flip-flops.
• Only one answer identifies the required clock condition.

Concept / Approach:With positive clocking, level-sensitive latches are transparent when clock is high; edge-triggered flip-flops capture data on the positive-going (rising) edge. Either interpretation maps to an active-high condition. This ensures consistent data capture and avoids hazards when combined with proper setup and hold timing.

Step-by-Step Solution:Interpret “positive clocking” as active-high behavior.Relate to device behavior: transparent or sampling when high/rising.Select “High” as the proper clock condition.

Verification / Alternative check:Data sheets for standard D flip-flops show a triangle symbol at the clock input for positive-edge devices, indicating sampling on the rising edge (active-high clocking), confirming the principle.

Why Other Options Are Wrong:Low: corresponds to negative/active-low clocking.Set: refers to asynchronous set input, not clock level.Race: undesired condition, not a valid clock requirement.None of the above: incorrect because “High” is correct.

Common Pitfalls:Mixing level-sensitive and edge-triggered interpretations; ignoring setup/hold times; failing to align clock domains leading to metastability.

Final Answer:High