Explanation
Correct answer: C.
Choice C is the best answer because it most logically completes the text’s discussion of the conservationists’ efforts to increase Azores bullfinch’s numbers. In this context, "successful" means accomplishing a goal or purpose. According to the text, conservationists planted more than 500,000 native trees in an Azores bullfinch habitat in order to boost the bird’s population size. The text then indicates that the population size did indeed grow as a result of the planted trees. Thus, in this context, the conservationists’ approach of planting native trees was successful because it achieved the goal of increasing the bird’s population size.
Why the other choices are wrong
Choice A
Choice A is incorrect because the text gives no indication that the conservationists’ approach of planting native trees to increase Azores bullfinch’s numbers was "amusing," or comical or entertaining. Instead, the approach was seriously undertaken and ultimately accomplished.
Choice B
Choice B is incorrect because the text doesn’t address how much it cost to achieve the goal of planting native trees to increase Azores bullfinch’s numbers. The text indicates that the approach was beneficial and successful rather than "costly," or expensive or harmful.
Choice D
Choice D is incorrect. According to the text, the conservationists’ approach of planting native trees to increase Azores bullfinch’s numbers was beneficial and successful rather than "disastrous," or damaging or unsuccessful.