Answer:
Your answer would be C.
Step-by-step explanation:
Sentence contains the participle phrase walking on the beach. A participle phrase will begin with a present or past participle. In this case, it begins with a present participle walking. As all phrases require two or more words, a participle phrase might include objects and/or modifiers that complete the thought (the PP on the beach).
Moreover, participle phrases always function as adjectives, adding description to the sentence. In the sentence above, the participle phrase modifies the noun Delores.