Explanation
Correct answer: D.
Choice D is the best answer. The convention being tested is punctuation use between a main clause and a supplementary phrase. In this choice, a colon is correctly used to mark the boundary between the main clause ("there...on") and the supplementary phrase ("openness to experience") and to introduce the information that identifies which personality trait participants scored especially high on.
Why the other choices are wrong
Choice A
Choice A is incorrect because it results in a rhetorically unacceptable sentence fragment beginning with "on" and separates a necessary preposition from the clause beginning with "there."
Choice B
Choice B is incorrect because a semicolon can’t be used in this way to join the main clause ("there...on") and the supplementary phrase ("openness to experience"). A semicolon is conventionally used to join two main clauses, whereas a colon is conventionally used to introduce an element that explains or amplifies the information in the preceding clause, making the colon the better choice in this context.
Choice C
Choice C is incorrect because it fails to mark the boundary between the main clause ("there...on") and the supplementary phrase ("openness to experience").