1. Correct Answer:
     Option D: All the options are equally good for the customer.
 2. Explanation:
     To determine which option is best for the customer, we need to calculate the final price the customer pays under each option. Let's assume the original price of the article is \( P \).
     Option 1:
         ○ Apply a 10% discount:
       New price = \( P \times (1 - 0.10) = 0.9P \)
         ○ Apply a 20% discount:
       New price = \( 0.9P \times (1 - 0.20) = 0.72P \)
         ○ Apply a 10% service tax:
       Final price = \( 0.72P \times (1 + 0.10) = 0.792P \)
     Option 2:
         ○ Apply a 20% discount:
       New price = \( P \times (1 - 0.20) = 0.8P \)
         ○ Apply a 10% discount:
       New price = \( 0.8P \times (1 - 0.10) = 0.72P \)
         ○ Apply a 10% service tax:
       Final price = \( 0.72P \times (1 + 0.10) = 0.792P \)
     Option 3:
         ○ Apply a 10% service tax:
       New price = \( P \times (1 + 0.10) = 1.1P \)
         ○ Apply a 20% discount:
       New price = \( 1.1P \times (1 - 0.20) = 0.88P \)
         ○ Apply a 10% discount:
       Final price = \( 0.88P \times (1 - 0.10) = 0.792P \)
     In all three options, the final price the customer pays is \( 0.792P \). Therefore, all options are equally good for the customer.