Correct Answer: a, b, c, d

Solution : Given:
a. Approach b. Appropriate c. Approval d. Approve

Step 1: Since all the words start with the same letter A , so move on to the next letter.
Step 2: The second, third, fourth, and fifth letters of each word are the same i.e., p , p , r , and o . So, move on to the next letter.
Step 3: Compare the sixth letter of (Appro a ch, Appro p riate, Appro v al, Appro v e). Approach will come before Appropriate, Approval, and Approve as a comes before p , and v according to the alphabetical system. Similarly, Appropriate will come before Approval and Approve as p comes before v according to the alphabetical system.
Step 4: Compare the seventh letter of (Approv a l, Approv e ). Approval will come before Approve as a comes before e according to the alphabetical system.

So, the sequence is Approach, Appropriate, Approval, Approve, or a, b, c, d. Hence, the fourth option is correct.