We can see here that the word that helps the reader understand the meaning of the phrase "bore into" is: B. "bud" (Line 7)
What is a phrase?
A phrase is a group of words that functions as a unit in a sentence. It does not contain a subject and a verb (as a clause does) and may consist of a single word or a combination of words that work together.
The phrase "ants bore into the peony bud" suggests that the ants are penetrating or digging into the peony bud, emphasizing the action of entering or making a hole within the bud. "Bore into" implies the action of digging or penetrating deeply into something, which is exemplified by the ants entering the peony bud in this context.