Male Dung Beetles Use Their Horn-Like Projections in Aggressive Interactions

Male dung beetles use their horn-like projections in aggressive interactions over nesting sites. What data suggested that sexual selection has influenced the evolution of these horns in dung beetles?

A) Horn size was correlated with body size.
B) A difference in horn size affected fight outcome.
C) An experimental reduction in horn size reduced breeding success.
D) An experimental increase in horn size enhanced breeding success.
E) Variation in horn size across populations was correlated with breeding success.