It does not make sense to use negative words, since there is no clue of using them.
the clue here is this last part of the sentence, the new mayor quickly accepts the sheriff requests.
We can describe the mayor to be helpful, and able to answer requests.
And also look at the word around the blank it is saying certain level of _______,
this also implies that sheriff expects a certain level of cooperation from the mayor however, he received more than what he expected.

I hope it helps

Although the sheriff had become accustomed to a certain level of__________from the town’s elected officials, he was still surprised by the way the new mayor quickly acceded to his requests.

prima facie if we read the prompt perfunctorily, we may be persuaded to mark B and D, but after observing closely. Answer will be A and C

there are 2 trigger words in the prompt. Although and Still surprised.
first trigger word Although gives a negative meaning , but still surprised negates that negative meaning and hence sentence overall becomes positive and hence deference and yielding will be the answer.
It is a perfect GRE types SE.

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