To identify the functions which best define the given sequence, we have to identify the number pattern.
The correct option is (a).
Given:
The given sequence is as follows,

<h3>What is an arithmetic sequence?</h3>
The arithmetic sequence define as the difference between two consecutive number would be same.
If we subtract 4 form each digit we will get next digit.
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So the function would be,

The option (b) and (d) show the increasing function whereas we have decreasing sequence.
Thus, the correct option is (a).
Learn more about arithmetic sequence here
:brainly.com/question/12637273