First, there is no conclusion in this. It’s not an argument — it’s just a set of facts. That’s usually the case for Must Be True questions.
Second, we can’t pick (A) because it discusses “the number of ski injuries.” We only learn about the percentage of ski injuries (0.9% of skiers got injured on the slopes in 1950, 0.3% of skiers got injured on the slopes in 1980, 10% of ski-injuries were in the resort and not the slopes in 1950, 25% of ski-injuries were in the resort and not the slopes in 1980). We can’t use premises that are only about percentages to prove conclusions about numbers. For instance, there could have been far more skiers on the slopes in 1980 compared to 1950. If that were true, the number of injuries on the slopes in 1980 might be greater than in 1950, even if the percentage of skiers injuried on the slopes went down in 1980.
Finally, (E) is corect because we know the there the percentage of slope injuries must be lower in 1980 (75% of all injuries at the resort) compared to 1950 (90% of all ski injuries at the resort).
