If the whole room chooses C, then every group gets a candy.

If one group votes D and the rest vote C, then the D group gets 5 candies

and the C groups each lose one. If everyone votes D, then every group loses 2 candies.

Table of Payoffs

C DD = -5 All D but you, you lose 5

D DD = -3 All D including you, you lose 3

C CD = -2 One group C with you C, you get -2

D CD = 1 One group C alone, you D, you get 1

C CC = 2 All groups C, you get 2

D CC = 5 All groups but you C, you D, you get 5