ANS:A - synchronous counters

Ring shift and Johnson counters are examples of asynchronous counters.

Answer is option B Asynchronous counters,

It's also known as ripple counters, and does not rely on a common clock signal to synchronize the state of their flip-flops.
Instead, the output of each flip-flop is used to trigger the next flip-flop in the sequence, which creates a ripple effect that propagates through the counter.

As a result, the output of an asynchronous counter may experience some propagation delay, which can cause glitches or other timing issues.