Select the letter-cluster that can replace the question mark (?) in the following series.
TXB, QWE, NVH, KUK, ?
Let's analyze the given series:
1. TXB - First letter: T - Second letter: X - Third letter: B
2. QWE - First letter: Q - Second letter: W - Third letter: E
3. NVH - First letter: N - Second letter: V - Third letter: H
4. KUK - First letter: K - Second letter: U - Third letter: K Now, look at the pattern for each position of the letters:
- The first letters follow the pattern: T, Q, N, K. This is a decreasing pattern by 3 (T → Q → N → K), so the next letter should be H.
- The second letters follow the pattern: X, W, V, U. This is a decreasing pattern by 1 (X → W → V → U), so the next letter should be T.
- The third letters follow the pattern: B, E, H, K. This is an increasing pattern by 3 (B → E → H → K), so the next letter should be N.
Thus, the correct answer is Option C (HTN).
If the roots of the quadratic equation \( ax^2 + bx + c = 0 \) are real and equal, then: