无码高清视频|成人自拍视频|欧美成人午夜无码A片秀色直播|草美女视频网站|美女被操网站在线观看

單項選擇題

A signal derived from a controlled function and returned to the initiating point is called a/an ().

A.monitoring signal
B.inverse signal
C.reverse signal
D.feedback signal

微信掃碼免費搜題