What Research Methods Did Pomfret and Knell (2006) Use to Examine

What research methods did Pomfret and Knell (2006) use to examine the role of sexual selection in dung beetles?

A) An experiment examining female choice of males with different horn sizes
B) An experiment that compared the fighting success of males of different body sizes competing for a female
C) Observations of mating success of males with differently sized horns
D) Observations of female choice of males of different sizes
E) An experiment that compared the fighting success of males with differently sized horns competing for a female