Select the combination of letters that when sequentially placed from left to right in the blanks of the given series will complete the letter series.
G _ _ A B G H I _ _ G _ I _ B _ H I _ B

Let's check the total number of letters and blanks.
The series has 20 positions: G _ _ A B | G H I _ _ | G _ I _ B | _ H I _ B

Let's try to divide it into 4 groups of 5 letters each:
Group 1: G _ _ A B
Group 2: G H I _ _
Group 3: G _ I _ B
Group 4: _ H I _ B

By comparing the groups:

Looking at Group 2 (G H I _ ) and Group 4 ( H I _ B), we can infer that the pattern is repeating or similar: G H I A B.

Let's test if each group is exactly G H I A B:

Group 1: G [H] [I] A B → Blanks: H, I

Group 2: G H I [A] [B] → Blanks: A, B

Group 3: G [H] I [A] B → Blanks: H, A

Group 4: [G] H I [A] B → Blanks: G, A

Let's list the filled letters in sequence: H, I, A, B, H, A, G, A.
This matches Option A perfectly.