Explanation
Correct answer: B.
Choice B is the best answer because as used in the text, "conceivable" most nearly means capable of being thought of or imagined. The text describes a journey that, despite being "insignificant in distance," was "by no means an easy one" because of the variety of obstacles that "nature had determined to throw…in the way." To emphasize the difficulty of the journey, the author portrays nature as actively scheming to present travelers with every obstacle that can be thought of—i.e., every imaginable obstacle.
Why the other choices are wrong
Choice A
Choice A is incorrect because in this context, "conceivable" does not mean obvious, or evident. Instead, by referring to "every conceivable obstacle," the text suggests a wide variety of challenges by evoking all the potential difficulties nature could present, not just those that the travelers might reasonably expect or foresee.
Choice C
Choice C is incorrect because in this context, "conceivable" does not mean straightforward, or easy to negotiate. The text is not indicating that the obstacles were simple to respond to and overcome. Rather, the text suggests that a wide range of obstacles made the journey difficult.
Choice D
Choice D is incorrect because in this context, "conceivable" does not mean uninterrupted. Although the text suggests that the obstacles were frequent and numerous, it does not emphasize the obstacles’ continuity; instead, the text conveys their unexpected variety and range.