Hi Elana,
Thanks for your question! I actually read answer choice (D) a bit differently.
Answer choice (D) says:
On average, it costs no less to feed a cat that eats fewer ounces of food per day than it does to feed a cat that eats more ounces of food per day.
Answer choice (D) does not specify whether the cat(s) are eating dry or wet food. If we read (D) literally, it appears to be saying that a cat who consumes 4 ounces of food per day costs the same to feed as a cat who consumes 6 ounces of food per day. We really have no way of assessing whether or not this is the case unless we know what type of food each cat is getting.
By contrast, your reasoning for answer choice (E) is on point. If canned food costs more per ounce than dry food, it can still cost more to feed a cat wet food than dry food even if they consume fewer ounces of wet food.
Best of luck studying!
Athena