In the following question, which one set of letters when sequentially placed at the gaps in the given series shall complete it:

FA_O_F_V_R_A_OR

Looking at the given series: $FA\_O\_F\_V\_R\_A\_OR$

We have 6 blank spaces to fill in this series.

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We need to find letters that will complete a repeating pattern when placed in the blanks.

Let me number the blanks:

$F A [1] O [2] F [3] V [4] R [5] A [6] O R$

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Let's fill in the blanks with VRAOFV in order:

Blank $[1] = V$

Blank $[2] = R$

Blank $[3] = A$

Blank $[4] = O$

Blank $[5] = F$

Blank $[6] = V$

This gives us: $F A V O R F A V O R F A V O R$

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Now let's break this into groups to see the pattern:

$FAVOR | FAVOR | FAVOR$

The word FAVOR repeats 3 times!

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The complete series is the word FAVOR written 3 times in a row.

Therefore, the answer is VRAOFV.

In these complete the series questions, always look for repeating words or patterns. Group the letters and see if they spell something familiar!