The effectiveness of an advertising campaign can be measured a. before, during, and after the campaign through the use of pretests, inquiries, and posttests. b. only before the campaign begins, to prevent unnecessary expenditures. c. during the campaign to determine whether more or less funds should be allocated, but not after the campaign. d. several weeks after the beginning of the campaign to determine whether the campaign is headed in the right direction. e. only after the campaign has been carried out completely and results have been tabulated.