The manager of a clothing store in the mall wants to collect data to find out customers' opinions of the brands of clothing sold at the store. Which group should he survey to collect the best data?

A.
twenty customers who asked to share their opinions of the clothing brands with the store manager
B.
twenty-five customers who visited the store but did not purchase any clothes
C.
thirty randomly selected customers who shopped at the clothing store
D.
forty randomly selected people in the mall parking lot