To solve this question, we need to identify the pattern or rule followed by the given series of letters: WFB, TGD, QHG. Let's break down the series and analyze it step by step.

1. Analysis of the first set: WFB
The first letter, W, is followed by the third letter, F, and then by the second letter, B. This pattern suggests that the letters are arranged in a reverse order from their original positions in the alphabet.

2. Analysis of the second set: TGD
Similar to the first set, the first letter, T, is followed by the third letter, G, and then by the second letter, D. Again, the letters are arranged in a reverse order from their original positions in the alphabet.

3. Analysis of the third set: QHG
Following the same pattern as the previous sets, the first letter, Q, is followed by the third letter, H, and then by the second letter, G. The letters are once again arranged in a reverse order from their original positions in the alphabet.

4. Identifying the pattern:
From the analysis of the given series, we can conclude that the letters in each set are arranged in reverse alphabetical order. Therefore, we need to continue this pattern to find the missing set.

5. Finding the missing set:
Starting with the letter N, which is the first letter of the missing set, we arrange the next two letters, H and J, in reverse alphabetical order. This gives us the set NHJ.

6. Selecting the correct option:
Among the given options (a) NHJ, (b) NHK, (c) NIJ, and (d) MIJ, the correct answer is option (c) NIJ, as it follows the established pattern of arranging the letters in reverse alphabetical order.

In summary, the correct answer to the series WFB, TGD, QHG, ? is NIJ (option c) as it continues the pattern of arranging the letters in reverse alphabetical order.