When Sherif Created Situations in Which the Warring Groups of the Eagles

When Sherif created situations in which the warring groups of the Eagles and the Rattlers had to cooperate to solve a problem with the water supply at the camp, he found that

A) cooperation between the two groups decreased hostility.
B) cooperation between the two groups did not decrease hostility.
C) cooperation between the two groups increased hostility.
D) cooperation between the two groups gave groups more of a chance to taunt one another.