Go-well Vitamins are made especially for teenagers. They make your skin shiny and clear. Mrs. J. Rice reports that her daughter's skin has improved dramatically, thanks to Go-well Vitamins. "I love what Go-well has done for me," Lily Rice confirms. Go-well is making teens happy throughout the Midwest. Bottles are flying off the shelves.
Why is the above claim about the vitamins unsupported by sufficient evidence?
a the passage includes references to emotions
b the passage centers on a personal testimonial
c the passage includes references to scientific research
d the passage uses a figure of speech in the last line