D. give up
Feedback keep off - 1. to prevent something from touching 2. to avoid eating something because it's not healthy 3. not to talk on certain subject especially if it is uncomfortable for someone. 4. not to get weight after loosing it.
let down - to upset.
knock off - 1. to stop working and go out 2. to reduce price 3. to make 4. to kill 5. to steal.
give up - to stop doing something, especially if you do it on regular basis