Which of the following flip-flops is free from race condition ?

Answer: Master-slave JK flip-flop

Why this is free from race condition:

• A master-slave JK flip-flop consists of two latches (master and slave) driven on opposite clock phases, so the master captures inputs while the slave is isolated, and the slave updates the output only after the master is closed.

• This separation prevents internal feedback from propagating back and forth during a single clock pulse, ensuring at most one state change per clock transition.

• Even when J and K are both 1 (toggling condition), the master-slave arrangement ensures a single toggle per clock edge rather than repeated toggling while the clock level remains active.

Why the other choices are not correct:

• T flip-flop: If implemented in a level-sensitive way, a constant T=1 can cause continuous toggling while the clock level is active, creating a race. Only edge-triggered/master-slave implementations avoid this.

• SR flip-flop: When both S and R are 1 the output is undefined, and changing inputs during an active level can produce hazards or race conditions.

Conclusion: The master-slave JK flip-flop’s two-phase (master then slave) operation prevents internal feedback during a single clock pulse, making it free from race condition among the listed options.