Which of the Following Is One of the Nine Principles

Which of the following is one of the nine principles of Positioning Advertising Copy Testing (PACT) ?

A) Provide measurements that are relevant to the objectives of the advertising.
B) Realize that the copy should be valid and that reliability may be too costly to guarantee.
C) Provide controls to increase the biasing effects of the ad content.
D) Use a convenience sample.
E) Realize that a single measurement is adequate to assess an ad's performance.