Answer: A) past
Step-by-step explanation: A participial phrase, is a group of words that begin with a present of past participle (for regular verbs if they are in present, they will end in -ing, and if they are past participles, they will end in -ed), after the verb, the participial phrase usually has modifiers (nouns, adjectives, etc) that help to complete the meaning of the phrase, in the given sentence the participial phrase is "established as a national park in 1930", the verb is "established" and it is in past form.