What type of counter is characterized by all flip-flops being clocked simultaneously?

A synchronous counter is defined by the fact that all flip-flops within the counter are clocked simultaneously by a common clock signal. This means that each flip-flop transitions from one state to the next at the same time, leading to a more predictable and stable performance in counting operations. This simultaneous triggering reduces propagation delay issues that can occur in other types of counters, particularly in asynchronous configurations.

In contrast, asynchronous counters clock their flip-flops at different times based on the output of the previous flip-flop, leading to a ripple effect that can introduce delays and potential counting inaccuracies due to this staggered response. Ripple counters are a specific type of asynchronous counter that rely on this cascading clocking method.

A decade counter is designed to count from 0 to 9 (ten states total) but can be either synchronous or asynchronous. The distinguishing feature of a decade counter itself isn't about how the flip-flops are clocked, but rather the range of values it counts.

Thus, the defining characteristic of a synchronous counter—where all flip-flops are clocked at the same instant—marks it as the correct answer to the question posed.