This is a repeat sign meaning to repeat the peice you just played. Your answer would be D.
Answer and Explanation:
Ask them to start coughing and attempt and remove the blockage, then ask them to try to spit the item out if it's in their mouth, don't place your fingers in their mouth because they may unintentionally bite you.
If this does not work, begin back blows (which moves onto severe choking).
I would put have my own teaching posters and strategies on 2 sides of the room and leave the other two for the other teacher