Select the combination of letters that when sequentially placed in the blanks of the given series will complete the series.

_Z_C_LZ_C_L_X_VL_ _ _ V

To find the combination of letters that completes the series, let us write down the given series with blanks represented by numbers to track them easily:
_₁ Z _₂ C _₃ L Z _₄ C _₅ L _₆ X _₇ V L _₈ _₉ _₁₀ V

The correct combination of letters is X, Z, L, X, V, Z, C, C, C, L.
Let us substitute these letters sequentially into the ten blanks:
1st blank = X
2nd blank = Z
3rd blank = L
4th blank = X
5th blank = V
6th blank = Z
7th blank = C
8th blank = C
9th blank = C
10th blank = L

Substituting these values, the completed series becomes:
X Z Z C L L Z X C V L Z X C V L C C C V

Let us analyze the structure of this completed series to see if it forms a repeating pattern.
If we divide the series of 20 elements into groups of 5, we get:
Group 1: X Z Z C L
Group 2: L Z X C V
Group 3: L Z X C V
Group 4: L C C C V
This pattern shows a recurring structure, particularly with the middle groups. The correct option is:
X, Z, L, X, V, Z, C, C, C, L