Answer:
A. The receding waves left a dark mark upon the golden sand.
Step-by-step explanation:
A participle is the verb form of a word that can serve as an adjective in a sentence or used to create the verb tense. In the chosen option above, the verb recede is used as a present participle because it is in the -ing form. It serves as an adjective because it describes the waves.
Participles of verbs can also exist in the past and -s form. In that case, recede is used as receded and recedes respectively.