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

Solution : Given:
1. Assemble 2. Astronomy 3. Assessment 4. Ascending 5. Assumption 6. Assurance

Step 1: Compare the first and second letters of each word. Since all the words start with the same letter A and are followed by s then move on to the next letter.
Step 2: The third letter of each word is c, s , or t . Based on the alphabetical order of these letters, we can arrange them –As c ending, As s emble, As s essment, As s umption, As s urance, As t ronomy.
Step 3: Compare the fifth letter of (Asse m ble, Asse s sment) and the fifth letter of (Assu m ption, Assu r ance). Asse m ble will come before Asse s sment in the sequence as m comes before s in the alphabetical system. Similarly, Assu m ption will come before Assu r ance as m comes before r .

So, the sequence is Ascending, Assemble, Assessment, Assumption, Assurance, Astronomy or 4,1, 3, 5, 6, 2. Hence, the fourth option is correct.