Afew graves in the cemetery were marked with crumbling tombstones; newer ones were outlined with brightly colored glass and broken coca-cola bottles. lightning rods guarding some graves denoted dead who rested uneasily; stumps of burned-out candles stood at the heads of infant graves.

in the excerpt above, what best describes the way in which the author is using a semicolon?

to connect two closely related clauses without a coordinating conjunction
to connect two closely related clauses with a conjunctive adverb
to connect two main clauses with complex internal punctuation
to clarify the meaning of phrases in a series