Explanation
Correct answer: B.
Choice B is the best answer. "Instead" logically signals that the information in this sentence—that Bartholdi decided to slim and tilt out the arm of the Statue of Liberty—contrasts with Eiffel’s design suggestions for the statue.
Why the other choices are wrong
Choice A
Choice A is incorrect because "additionally" illogically suggests that the information in this sentence is merely an additional fact related to Eiffel’s design suggestions in the previous sentence. Instead, it contrasts with those suggestions.
Choice C
Choice C is incorrect because "thus" illogically signals that the information that follows is a result of Eiffel’s design suggestions in the previous sentence. Instead, it contrasts with those suggestions.
Choice D
Choice D is incorrect because "for example" illogically signals that the information about Bartholdi’s design decisions in this sentence exemplifies Eiffel’s design suggestions in the previous sentence. Instead, it contrasts with those suggestions.