Official ExplanationRead the Original Sentence Carefully, Looking for Errors:
The intention of the sentence is to convey several of the items that "mostly" comprise the diet of bears and the one item, salmon, that is only an occasional part of that diet. The sentence as written incorrectly modifies a noun, salmon, with the adverb occasionally. Eliminate (A).
Scan and Group the Answer Choices:
There is no obvious pattern in the remaining choices, so analyze them carefully one by one.
Eliminate Choices Until Only One Remains:
Eliminate (B). While it correctly uses "occasionally" to modify the verb "is," it does not convey a complete idea.
Eliminate (C) and (D). They also do not convey complete ideas.
(E) is correct. It correctly separates "salmon," the occasional meal, from the items in the bear's usual diet by the use of the conjunction "with." It also properly structures "salmon as an occasional meal" as a noun phrase parallel to the other nouns in the list of diet items.
TAKEAWAY: Adjectives modify nouns, adverbs modify verbs and adjectives.