Star drilling company produces auger-a moving device used in mines. in a recent advertisement, the firm featured the president of the national mining association stating, "i can guarantee the performance of star augers." this is an example of:

A testimonial.

In promotion and of advertising, a testimonial or show consists of a person's written or spoken statement extolling the virtue of a product. The term "testimonial" most commonly applies to the sales-pitches attributed to ordinary citizens, whereas the word "endorsement" usually applies to pitches by celebrities.