Correct Answer: 3, 5, 2, 1, 6, 4

Solution : Given:
1. Realistic 2. Readily 3. Reach 4. Really 5. Reactor 6. Realize

Step 1: Compare the first, second, and third letters of each word. Since all the words start with the same letter R and are followed by e and a , then move on to the next letter.
Step 2: The fourth letter of each word is either c , d , or l . Based on the alphabetical order of these letters, we can arrange them – Rea c h, Rea c tor, Rea d ily, Rea l istic, Rea l ly, Rea l ize.
Step 3: Compare the fifth letter of (Reac h , Reac t or) and the fifth letter of (Real i stic, Real l y, Real i ze). Reac h will come before Reac t or in the sequence as h comes before t in the alphabetical system. Similarly, Real i stic and Real i ze will come before Real l y as i comes before l .
Step 4: Compare the sixth letter of (Reali s tic, Reali z e). Reali s tic will come before Reali z e in the sequence as s comes before z in the alphabetical system.

So, the sequence is Reach, Reactor, Readily, Realistic, Realize, Really, or 3, 5, 2, 1, 6, 4. Hence, the second option is correct.