You Want to Test Charles Darwin's Prediction That an Orchid

You want to test Charles Darwin's prediction that an orchid with long pollen tubes has a pollinator with long,thin mouthparts that can reach the bottom of the elongated nectar tube.You place nets over some orchids,which allows pollinators with small,short mouthparts to enter but prevents the entry of pollinators with long,thin mouthparts.Next,you compare the number of seeds produced by plants with and without the nets.In this experiment,seed production is a(n)  

A) dependent variable.
B) hypothesis.
C) theory.
D) independent variable.
E) standardized variable.