<p>Soon after the first visitors arrived, increasing numbers of the residents of the remote island thought it possible that the outside world, instead of being <em>__, could be </em> and worth exploring.</p>
<p>Why is the answer D and not A, insular and unlimited work well in the contrast for “instead of being, could be”</p>
<p>if the residents lived on a remote island, they wouldn’t have been hesitant to explore an insular place</p>
<p>I think you’re taking the fact that the residents saw visitors indicated to them that their island wasn’t the only thing in the world; that there were outside lands in addition to theirs, and that was why they no longer saw the world as “insular.” But the phrase right before the first blank refers specifically to the outside world; it was the outside world that you’re saying they no longer viewed as insular. This doesn’t make sense - for insular to work, the blank would need to refer to the world in general, since it was their island that they viewed as insular. But it doesn’t make sense for them to think the outside world was like an island. Basically, it wasn’t the outside world they viewed as insular, it was their own world.</p>
<p>I hope that explanation makes sense. While you could force A to work, D is just a better answer.</p>
<p>Yeah I kinda understand it, it’s just there’s no hint or foremention that they think the outside world is threatening nor does fascinating corrolate to threatening at all.</p>
<p>True. On the other hand, fascinating implies “worth exploring” much more than unlimited does. And threatening would indicate that they previously didn’t want to explore it, while insular doesn’t really fit. So while there is more parallelism between insular-unlimited, I think the words threatening-fascinating fit better in the context.</p>