In the Section "Investigating Life: the Battle for Position in Cacao

In the section "Investigating Life: The Battle for Position in Cacao Tree Leaves",what was the dependent variable?

A) the age of the leaf
B) the percent of the leaf area damaged
C) the presence or absence of endophyte spores
D) the presence or absence of the pathogen Phytophthora
E) the percent of the leaf area containing endophytes