Find the missing group of letters in the following series: BC, FGH, LMNO, _____

The correct option is TUVWX.

Let us analyze the given series step-by-step to find the pattern:
The series is: BC, FGH, LMNO, _____

Step 1: Analyze the number of letters in each group
- The first group "BC" has 2 letters.
- The second group "FGH" has 3 letters.
- The third group "LMNO" has 4 letters.
Following this progression, the missing group must have 5 letters.

Step 2: Analyze the gaps between consecutive letter groups
Let's look at the letters that are skipped between the end of one group and the start of the next:
- Between the first group "BC" and the second group "FGH", the skipped letters are D and E (2 skipped letters).
- Between the second group "FGH" and the third group "LMNO", the skipped letters are I, J, and K (3 skipped letters).
Following this pattern, the number of skipped letters between the third group and the missing group should be 4.

Step 3: Determine the missing group
- The third group ends with the letter O.
- Skipping the next 4 letters in alphabetical order (P, Q, R, and S), the next group must start with the letter T.
- Since the missing group must consist of 5 consecutive alphabetical letters starting with T, we get: T, U, V, W, X.

Therefore, the missing group of letters in the series is TUVWX.