Question

Read the sentence.

When they arrived at the beach, the students who had never seen the ocean before ran toward the shore.

Which part of the sentence is an adverbial dependent clause?

when they arrived at the beach
the students who had never seen
the ocean before
ran toward the shore

Answer 1

"when they arrived at the beach"

It's an adverbial (subordinate) clause of time — introduced by "when," modifies "ran," and cannot stand alone as a sentence.