The stem asks us the point on which the physician and the enthusiast disagree.

A is wrong because the enthusiast doesn't deny the significant number of injuries

B can be eliminated for clearly because "home trampolines" and the injuries caused by them isn't a topic being debated by both our participants. Only the enthusiast brings it up.

C is wrong because nowhere is the mention of declining injuries per user

D is a tempting choice. Considering the fact that both the participants discuss professional supervision one might be tricked into selecting this option. However the Physician does not explicitly say that this will reduce injuries

E is the clear winner in my humble opinion , since one side says professional supervision is necessary while the other points out that injuries will occur nonetheless.

Waiting for OA.

(A) trampolines cause injuries to a significant number of people using them -
P: Definitely agrees to this fact
TE: Agrees. He/She simply mentions that the injuries/sales percentage have decreased over years

(B) home trampolines are the main source of trampoline-related injuries
Both do not comment on "main-source"

(C) the rate of trampoline-related injuries, in terms of the number of injuries per trampoline user, is declining
P: He/she does not comment on the number of injuries/user. Simply states that there are considerable injuries because of the use of trampoline
TE: Agrees to this fact

(D) professional supervision of trampoline use tends to reduce the number of trampoline-related injuries
P: Comments that the used is advised. Does not comment on the injuries rate in presence of supervision
TE: Similar to P, does not comment on the injuries rate in presence of supervision

(E) trampoline use is an activity that warrants mandatory professional supervision
P: Mentions that the high number of accidents dictates that trampoline use requires supervision
TE: Disagrees by mentioning that the data mentioned does not provide the complete picture.

Answer: E