For an edge-triggered D flip-flop, 对边沿触发的D触发器，

A、a change in the state of the flip-flop can occur only at a clock pulse. 触发器状态的改变仅在时钟脉冲处发生。

B、The state that the flip-flop goes to depends on the D input. 触发器的状态如何转换由D输入端决定。

C、The output follows the D input at each clock pulse. 每个时钟脉冲处，输出都跟随输入D变化。

D、All of these answers. 所有答案都对。