Study the poster showing characters from the movie Star Wars and created by the US Department of Health, Education, and Welfare in 1977.
How does the poster most likely demonstrate the use of the testimonial technique ?
The photograph shows fictional film characters, used to
"sell' immunization,
The text references the health department, a revered
government institution.
The phrase "call your doctor" adds a reference to an
esteemed authority.
The phrase "parents of Earth" reminds the audience of
the importance of parenting.

A testimonial is one of the most common and effective advertising techniques. You may notice that the products you've been using are endorsed by either famous celebrities or satisfied customers, giving their feedback about the product. In other cases, some promotional ads use experts' opinions about the product. These are examples of testimonials.

In this case, the US Department of Health, Education, and Welfare use Star Wars' characters to sell the idea of immunization.

In 1977, the first installment of Star Wars was released, and it was a certified box office. The irony illustrates that the two characters were not human beings, but they're warning humans regarding immunization. It may sound funny, but people bought it. And it's because of the characters in the poster.

R2D2 and C3P0 were the characters used in the poster who played supporting but remarkable roles in the movie franchise. The creators of the poster took advantage of how famous these two were and cited as likeable sources since many people loved them.