In an up-counter, which flip-flop is incremented by one when a trigger is applied?

The least significant digit (LSD) flip-flop is the correct choice as it is the first in the sequence of flip-flops to be incremented when a trigger is applied in an up-counter. An up-counter operates by adding one to its current count each time it receives a clock pulse (the triggering signal). In this counting mechanism, the LSD is responsible for the incrementing action first because it represents the lowest binary place value.

When a clock pulse is applied to the LSD flip-flop, it toggles between its two states (0 and 1) based on the incoming pulses. The changes in the LSD will affect the subsequent flip-flops in the counting sequence as they reach their trigger thresholds, but the primary increment initiated by the clock action occurs at the LSD. This characteristic allows the flip-flops to accurately count in binary as each subsequent flip-flop corresponds to a higher value.

In contrast, the other flip-flops mentioned serve different functions: the most significant digit (MSD) flip-flop represents the highest place value and is only toggled based on the state of the LSD and other flip-flops, the master reset flip-flop is used to reset the counter to a predefined state, and the clock pulse