What are the effects of repeated exposure to an advertising message? The answer may depend on both the length of the ad and how often it is repeated. And experiment investigated this question using...

What are the effects of repeated exposure to an advertising  message? The answer may depend on both the length of the ad and how often it is repeated. And experiment investigated this question using undergraduate students. All students viewed a 40 minute television program that included ads for a new smartphone. Some subjects saw a 30-second commercial others, a 90-second commercial. The same commercial was shown either one, three, or 5 times during the program. After viewing, all students answered questions about there recall of the ad, their attitudes towards the smartphone, and there intentions to purchase it. In this experiment, the length of the commercial and the number of times it was shown are.

(A) the responses.

(B) the blocking variables.

(C) lurking variables.

(D) the explanatory variables.