Pulse Train and Frequency
- A pulse train is a series of pulses with a specific frequency.
- The frequency of a pulse train is the number of pulses it contains per unit of time.
- In this case, the pulse train has a frequency of 1MHz, which means it contains 1 million pulses per second.

Mod-1024 Ripple Counter
- A ripple counter is a type of digital circuit that counts the number of pulses in a pulse train.
- In a mod-1024 ripple counter, the counter will reset to zero after counting 1024 pulses.
- The counter is built using J-K flip-flops, which are basic building blocks of digital circuits.

Propagation Delay
- Propagation delay is the time it takes for a signal to travel from the input of a circuit to the output.
- In the case of a ripple counter, the propagation delay refers to the time it takes for a pulse to propagate through each flip-flop stage of the counter.

Maximum Permissible Propagation Delay
- The maximum permissible propagation delay per flip-flop stage is the maximum amount of time it can take for a pulse to propagate through each stage and still maintain proper operation of the counter.
- If the propagation delay exceeds this maximum value, the pulses may not be counted accurately and the counter may not function correctly.

Answer
- The correct answer is option 'B', which states that the maximum permissible propagation delay per flip-flop stage is 100 ns.
- This means that the pulse must propagate through each flip-flop stage within 100 ns in order for the counter to operate properly.

Explanation
- The frequency of the pulse train is 1MHz, which means each pulse has a time period of 1µs (1/1MHz = 1µs).
- In order for the counter to count accurately, each flip-flop stage must complete its operation within the time period of each pulse.
- The counter has 1024 stages, so the time available for each stage is 1µs / 1024 = 976.5625 ns.
- Since the maximum permissible propagation delay per flip-flop stage is given as 100 ns, which is less than the available time of 976.5625 ns, the counter will function correctly.
- If the propagation delay per flip-flop stage exceeds 100 ns, the pulses may not propagate through the stages fast enough, and the counter may not count accurately.
- Therefore, the maximum permissible propagation delay per flip-flop stage is 100 ns for proper operation of the mod-1024 ripple counter.