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

Solution : Given:
1. Strategy 2. Strength 3. Stranger 4. Stretch 5. Struggle 6. Strange

Step 1: Compare the first letter of each word. Since all the words start with the same letter S , we move on to the next letter.
Step 2: Let's move to the second letter of each word. Since all the words have the same second and third letters t and r , we move on to the next letter.
Step 3: The fourth letter of each word is: a, e, a, e, u, a . Based on the alphabetical order of these letters, we can arrange them: Str a tegy, Str e ngth, Str a nger, Str e tch, Str u ggle, Str a nge.
Step 4: Compare the next letter of (Stra t egy, Stra n ger, Stra n ge) and (Stre n gth, Stre t ch). Strength will come before Stretch in the sequence as n comes before t in the alphabetical system.
Step 5: Compare the next letter of (Stranger, Strange). Strange will come before Stranger in the sequence as all the letters of the word Stranger are the same as Strange.

So, the sequence is Strange, Stranger, Strategy, Strength, Stretch, Struggle or 631245. Hence, the fourth option is correct.