Explanation
Correct answer: A.
Choice A is the best answer because as used in the text, "supported" most nearly means held up or sustained physically. The sentence describes the physical structure of the Panhandle bridge, stating it was "supported by massive sandstone pillars." This clearly refers to the structural relationship between the bridge and its pillars—the pillars physically hold up the bridge and keep it standing. The text further emphasizes the physical nature of this support by describing the pillars as "stalwart" (strong and sturdy) and noting they’ve been performing this function for fifty years.
Why the other choices are wrong
Choice B
Choice B is incorrect. Although in some contexts "supported" can mean "encouraged," the sandstone pillars and bridge described in the text are all inanimate objects that can’t provide or receive encouragement. The text clearly describes a structural relationship between the elements of the bridge, not an emotional one.
Choice C
Choice C is incorrect. Although in some contexts "supported" has a meaning similar to "improved on," the text doesn’t suggest that the sandstone pillars have enhanced or made the bridge better; rather, they simply provide the necessary physical foundation to keep the bridge standing. Thus, the sentence describes the structural elements of the bridge, not improvements made to it.
Choice D
Choice D is incorrect. Although in some contexts "supported" can mean "defended," the text doesn’t present a situation in which the sandstone pillars are defending the bridge from a threat. Instead, the description focuses on the physical structure of the bridge, in which the pillars hold the bridge up and ensure its stability.