Final answer:
The correct word to complete the sentence is 'fatuous,' as it contrasts with 'astute' and fits the description of the committee's report being an incongruous mixture.
Step-by-step explanation:
The student's question requires choosing the word that appropriately completes the sentence. The sentence describes a committee's report as being a mix of the astute (which means clever or insightful) and another characteristic that contrasts with astute. The options given are 'irrefutable' (which means impossible to deny or disprove) and 'fatuous' (which means silly and pointless). As 'irrefutable' does not contrast with 'astute' in the negative way that the sentence suggests, 'fatuous' is the correct answer. Therefore, the complete sentence should read: 'Not surprisingly, the committee’s final report was an incongruous mixture of the astute and the fatuous.'