(Please explain your answer and why other options are not correct) A clothing retailer recently streamlined its online ordering process in an effort to drive more sales. A four-week broadly targeted digital campaign was launched across Facebook, YouTube, display and programmatic video to promote the recent changes. The client is interested in determining high-performing conversion paths to develop a sequencing strategy moving forward.

What measurement approach should be used to determine the success of the campaign?

A. Pre and post survey

B. Randomized control trial

C. Attribution

D. A/B test