Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series.ABZ, BCY, CDX, DEW, _ _ _

Let's analyze the pattern of each letter position in the triplets:First letter of each cluster:A $\to$ B (+1)B $\to$ C (+1)C $\to$ D (+1)D $\to$ E (+1)The first letter of the missing cluster must be E.Second letter of each cluster:B $\to$ C (+1)C $\to$ D (+1)D $\to$ E (+1)E $\to$ F (+1)The second letter of the missing cluster must be F.Third letter of each cluster:Z $\to$ Y (-1)Y $\to$ X (-1)X $\to$ W (-1)W $\to$ V (-1)The third letter of the missing cluster must be V.Combining these together, the next cluster in the series is EFV.