Megan enabled Conversion Optimizer in all six of her campaigns. How can she tell if Conversion Optimizer is improving campaign performance

Megan enabled Conversion Optimizer in all six of her campaigns. How can she tell if Conversion Optimizer is improving campaign performance 

A) Monitor overall changes in clicks received
B) Enable and disable Conversion Optimizer every other day to observer differences
C) Compare average CPA and conversion rate before and after using Conversion Optimizer 
D) Install new Conversion Tracking code