The italicized portion of the sentence is "addressed to my sister."
Answer: C) past participial phrase.
Explanation: A participle is a verbal form that ends in "-ing" (present) or -ed, -en, -d, -t, -n, or -ne (past), it can act as an adjective, modifying a noun or pronoun. A participial phrase consists of a participle plus modifiers or objects. In the given sentence, we can see an example of a past participial phrase, with the past participle "addressed" and the object "to my sister," notice that it acts like an adjective that modifies the noun "package."
