Select the option that represents the letters which, when placed sequentially from left to right in the following letter-series, will complete the series.
L _ H _ _ L K H C _ _ K H _ _ L _ H C W

The given series consists of 20 elements. Let's try breaking it down into 4 groups of 5 letters each:
L _ H _ _ | L K H C _ | _ K H _ _ | L _ H C W

By comparing the second group (L K H C _) and the fourth group (L _ H C W), we can easily infer the repeating 5-letter pattern pattern to be L K H C W.

Let's apply this pattern across all 4 blocks:

First block: L [K] H [C] [W] → Filled letters: K, C, W

Second block: L K H C [W] → Filled letter: W

Third block: [L] K H [C] [W] → Filled letters: L, C, W

Fourth block: L [K] H C W → Filled letter: K

Combining all the filled blanks in sequence: K C W W L C W K.