What statement in the passage weakens the argument that personal music players cause hearing loss?

Experts say more research is needed to prove a definite link between portable music and DVD players and hearing loss.

Twenty-nine percent of students reported saying "what" or "huh" during conversations compared with 21 percent of adults.

Seventeen percent of students and 12 percent of adults said they have heard ringing in their ears

"Many kids who are using this type of technology are plugging virtual rock concerts into their ears," said Pam Mason of the ASHA.

And your answer is?