From the choices provided, select the pair of words that best fills the blanks to complete the sentence meaningfully.

Several of the astronomy students found the ____________________ hypothesis difficult to _____________________.

The correct option is abstruse, comprehend.

To complete the sentence meaningfully, let's analyze the context and the meanings of the words provided in the choices.

Sentence: "Several of the astronomy students found the ____________________ hypothesis difficult to _____________________."

1. The first blank describes the nature of the "hypothesis".
2. The second blank describes what the students found difficult to do with such a hypothesis.

Let's examine the meaning of the correct pair of words:

• Abstruse means difficult to understand, obscure, or esoteric. This fits logically as a description of a complex astronomy hypothesis.
• Comprehend means to grasp mentally or understand. This fits logically as the action that students would find difficult when dealing with an abstruse hypothesis.

Thus, placing abstruse and comprehend into the blanks yields a clear and coherent sentence: "Several of the astronomy students found the abstruse hypothesis difficult to comprehend."

Let's briefly evaluate why the other options are incorrect:

• implacable, permeable: "Implacable" (relentless/unstoppable) does not describe a hypothesis, and "permeable" (allowing liquids or gases to pass through) makes no sense in this context.
• eclectic, resolute: "Eclectic" (deriving ideas/style from a broad range of sources) does not logically connect to being difficult to be "resolute" (admirably purposeful/determined).
• subordinate, willed: "Subordinate" (lower in rank) and "willed" do not fit the context of students trying to understand a scientific theory.
• obtuse, permeable: While "obtuse" can mean difficult to understand in some contexts, it usually describes a person who is slow to understand, not a hypothesis itself; furthermore, "permeable" is incorrect.