Choice D is the best answer. “Second” logically signals that the information in this sentence—that the effort to bury the ship would likely only have been made for a king—joins the information in the previous sentence (“first…”) in supporting Brunning’s claim that the burial site was likely the tomb of a king.

Choice A is incorrect because “instead” illogically signals that the information in this sentence presents an alternative or substitute to the previous information about the gold artifacts inside the ship. Rather, this sentence presents a second piece of information that supports Brunning’s claim. Choice B is incorrect because “still” illogically signals that the information in this sentence exists in contrast to or despite the previous information about the gold artifacts inside the ship. Instead, this sentence presents a second piece of information that supports Brunning’s claim. Choice C is incorrect because “specifically” illogically signals that the information in this sentence specifies or elaborates on the previous information about the gold artifacts inside the ship. Instead, this sentence presents a second piece of information that supports Brunning’s claim.