Correct Answer: 4, 1, 3, 2

Solution : Given:
1. Complicate 2. Complicity 3. Complication 4. Complaint

Step 1: Compare the first letter of each word. Since all the words start with the same letter C, then move on to the next letter.
Step 2: The second, third, fourth, and fifth letters of each word are the same, i.e., o, m, p, and l, then move on to the next letter.
Step 3: The sixth letter of each word is either i or a. Based on the alphabetical order of these letters, we can arrange them – Complaint, Complicate, Complicity, Complication
Step 4: The seventh letter of (Complicate, Complicity, Complication) are the same, so move on to the next letter.
Step 5: Compare the eighth letter of (Complicate, Complicity, Complication). (Complicate, Complication) will come before Complicity as a comes before i in alphabetical order.
Step 6: The ninth letter of Complicate and Complication are the same, so move on to the next letter.
Step 7: Compare the tenth letter of Complicate and Complication. Complicate will come before Complication as e comes before i in alphabetical order.

So, the sequence is Complaint, Complicate, Complication, Complicity, or 4, 1, 3, 2. Hence, the third option is correct.