Answer:
where old coral reefs rose above the sea.
Explanation:
Adverb clauses are dependent clauses which contain a subordinating conjunction and indicate how, when, where and why the action is performed. Other subordinating conjunctions used in adverb clauses are if, before, because and in order that. Thus, in the sentence given, the adverb clause functions as an adverb clause of place and describes where the Palau Islands are located in the North Pacific Ocean.
