The structure of the key switch is usually a mechanical elastic element. When the key is pressed and opened, the contact will be unstable at the moment of closing and opening. In order to eliminate the adverse consequences caused by jitter, the methods often used are () .

A. Hardware de-bouncing(去抖动)
B. Software de-bouncing
C. , hardware and software two methods
D. Mono-stable circuit(单稳态电路) de-bouncing method