Given that the conditions in binary star systems should make planetary formation nearly impossible, it’s not surprising that
the existence of planets in such systems has lacked ______ explanation. Roman Raﬁkov and Kedron Silsbee shed light on the
subject when they used modeling to determine a complex set of factors that could support planets’ development.
a discernible
a straightforward
an inconclusive
an unbiased
Choice B is the best answer because it most logically completes the text’s description of efforts to explain the existence of
planets in binary star systems. As used in this context, describing an explanation as “a straightforward” one would mean that
the explanation is direct and uncomplicated. The text asserts that since it should be “nearly impossible” for planets to form
in binary star systems, it’s “not surprising” that there isn’t a straightforward explanation for the existence of planets in such
systems; the fact that one potential approach involves “complex” factors offers further contextual support for this idea.
Choice A is incorrect because it would not make sense in context to say that there isn’t “a discernible” explanation—meaning
an explanation capable of being perceived—for the existence of planets in binary star systems. The text discusses just such
an explanation offered by Roman Raﬁkov and Kedron Silsbee, which indicates that their explanation can be
discerned. Choice C is incorrect because the text emphasizes how diﬃcult it is to explain the existence of planets in binary
star systems, suggesting that the situation isn’t marked by the lack of “an inconclusive” explanation—an explanation that
does not resolve the issue—but rather that if any explanations have been offered, they’ve likely been inconclusive
ones. Choice D is incorrect because nothing in the text suggests that there is a lack of “an unbiased,” or impartial and
unprejudiced, explanation for the existence of planets in binary star systems. The text indicates that it’s diﬃcult to explain
the existence of planets in such systems and it describes one attempt to do so, but there is no evidence that explanations
from Roman Raﬁkov and Kedron Silsbee or others are biased.