LSAT28-19, help~

19. Over the past 20 years, skiing has become a relatively safe sport due to improvement in ski equipment. There has been a 50 percent drop in the number of ski injuries over the last 20 years. Clearly, however, there have not been decreases in the number of injuries in all categories, as statistical data readily show, for although broken legs and ankle injuries have decreased by an astounding 90 percent, knee injuries now represent 16 percent of all ski injuries, up significantly from the 11 percent of 20 years ago.

The reasoning in the argument is flawed because the argument does which one of the following?
(A) It fails to allow for there being ski injuries other than broken legs, ankle injuries, and knee injuries.
(B) It infers disparate effects from the same single cause.
(C) It ignores the possibility that the number of skiers has increased over the past 20 years.
(D) It assumes that an increase in the proportion of knee injuries rules out a decrease in the number of knee injuries.
(E) It proceeds as though there could be a greater decease in injuries in each category of injury than there is in injuries overall.

plz have a look first.

D

Knee injuries的比例增多了，但是数量却是减少的。