Explanation
Correct answer: D.
Choice D is the best answer. “Actually” logically signals that the information in this sentence—that the entry fee is charged per person—corrects the assumption described in the previous sentence that the fee is charged per vehicle.
Why the other choices are wrong
Choice A
Choice A is incorrect because “consequently” illogically signals that the fee being charged per person is a consequence of visitors assuming the fee is charged per vehicle. Instead, the sentence corrects that assumption.
Choice B
Choice B is incorrect because “second” illogically signals that the fee being charged per person is a second point in a series following the previous information about what visitors assume. Instead, the sentence corrects that assumption.
Choice C
Choice C is incorrect because “moreover” illogically signals that the fee being charged per person is merely an additional fact related to the previous information about what visitors assume. Instead, the sentence corrects that assumption.