Explanation
Correct answer: D.
Choice D is the best answer because it most logically completes the text’s discussion of how a data-transfer project affected data from equipment from the Apollo Moon landings. In this context, "available" means accessible or able to be used. The text explains that the Apollo equipment is still on the Moon, but the data it collected "were mostly inaccessible" until a data-transfer project was undertaken. The text then states that this project allowed a researcher to use the information that has been collected. This context makes it clear that the project made previously inaccessible data available, or accessible.
Why the other choices are wrong
Choice A
Choice A is incorrect because saying that a project made data from the Apollo equipment on the Moon "predictable" would mean that the data could be known or declared in advance, and it’s not clear how that would be achieved, particularly with data that had been "mostly inaccessible" before the project. Rather than suggesting that the data-transfer project made the data predictable, the text conveys that it made the data available to be used as sources of information.
Choice B
Choice B is incorrect because the sentence indicates that data from the Apollo equipment on the Moon were "mostly inaccessible" until a recent data-transfer project did something to them, after which a researcher was able to make use of the data. This context conveys that the project made the data accessible and usable, not that it made them "complicated," or complex or difficult to understand.
Choice C
Choice C is incorrect. In this context, "representative" would mean either standing as a symbol of something or serving as a typical example from a group, and the text gives no indication that data retrieved from the Apollo equipment on the Moon was merely an example or symbolic. Rather, the text focuses on the availability and usefulness of the data, indicating that a data-transfer project enabled a researcher to use data that had previously been "mostly inaccessible."