What evidence did Chapman and Chapman (2000) use to conclude that competition limits group size in the primates they studied?

What evidence did Chapman and Chapman (2000) use to conclude that competition limits group size in the primates they studied?

-They found a positive correlation between group size and the density of food trees

-They observed a decline in group size with natural decline in food availability

-They observed an increase in group size with the experimental addition of food

-They observed an increase in fitness of individuals with a decline in group size

-They observed an increase in group size with an experimental reduction in competitors