Which of the following flip-flops, in its standard level-clocked form, does…

Concept: Race-around is a hazard specific to level-clocked flip-flops whose CURRENT output feeds back into the gating/excitation logic that decides whether to toggle AGAIN. If the active clock level stays high longer than the internal gate propagation delay, that live feedback lets the output re-trigger and toggle repeatedly within the same clock pulse. This is a narrower condition than "the circuit contains feedback somewhere" — a storage latch's cross-coupled gates also feed back, but only to hold a value, not to decide a fresh toggle.

Application: Check each of the four flip-flop types (in their plain, level-clocked form — the standard reading for this classic question) for that specific output-into-gating-logic feedback:

• T flip-flop — logically a JK with J = K = T tied together; its output feeds back into the gating logic that decides the next toggle, so while T = 1 stays active it keeps re-triggering for as long as the clock level is high.

• JK flip-flop — with J = K = 1 held through the active clock level, the output feeds back into the gating logic and re-triggers repeatedly; this is the textbook race-around case.

• Clocked RS flip-flop — its cross-coupled gates feed back only to hold (store) the latched value, not to decide a fresh toggle, so it cannot show JK/T-style race-around; but it has its own separate hazard — asserting then releasing S = R = 1 sends those same cross-coupled gates racing against each other's propagation delay, leaving an unpredictable final output.

• Clocked D flip-flop — its internal storage feedback holds the sampled state, while the next state comes directly from D rather than from an output-fed toggle-decision path.

Cross-check: Race-around specifically needs the CURRENT output to feed back into the logic that decides whether to toggle again, while the clock is still active. Clocked D has no output-fed toggle-decision path, and clocked RS's cross-coupled feedback only holds a value rather than re-deciding a toggle — so neither shows JK/T-style race-around. But RS is not hazard-free either: its own S = R = 1 condition creates a genuine (if differently-named) instability. Clocked D is the only option among the four without an output-fed toggle-decision path or an invalid input combination, which is why it is the one flip-flop here inherently free of the race-around condition. Note the option list also names plain “T flip-flop” and plain “JK flip-flop” — not a master–slave or edge-triggered version — so the race-around hazard stays attached to them.