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 – Compl a int, Compl i cate, Compl i city, Compl i cation
Step 4: The seventh letter of (Compli c ate, Compli c ity, Compli c ation) are the same, so move on to the next letter.
Step 5: Compare the eighth letter of (Complic a te, Complic i ty, Complic a tion). (Complicate, Complication) will come before Complicity as a comes before i in alphabetical order.
Step 6: The ninth letter of Complica t e and Complica t ion are the same, so move on to the next letter.
Step 7: Compare the tenth letter of Complicat e and Complicat i on. 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.