As structured, this stimulus appears to be a response to someone having said something like "we should define 'intelligent life.'" In response, the author of the stimulus explains why efforts to define intelligent life may be futile - "it is likely we will find and recognize intelligent life elsewhere in the universe only if we leave our definitions open to new, unimagined possibilities." This is why answer choice (D) is correct).
Answer choice (C) is incorrect because the author of this stimulus is not so much saying that "'intelligent life' cannot be adequately defined," but rather that efforts to define the term may backfire by being too narrow, too unimaginative, too rooted in what is already known.
Hope this helps! Please let us know if you have any additional questions.
RyanSpencerMay 2, 2019
@mehran thanks for your explanation. I too was confused about C, your explanation makes perfect senes.
The author is not saying that intelligent cannot be correctly defined, he is simply saying that for this particular situation, defining it would not help them find intelligent life.
