A. kept in
Feedback let up - 1. to become less severe 2. to make less effort.
keep in -1. to make somebody stay in hospital because of their health 2. to make somebody stay at home as a punishment.
fall about - to burst out laughing.
let out - 1. to make a loud sound 2. to loosen a piece of clothing 3. to take money from somebody for a rent 4. to set somebody free