The correct answer is ‘The Most’. Key Points Let’s consider the following points- In the given context, the underlined word a more will be replaced with most. It is because ‘dress’ is expensive as compared to all the other dresses, so, ‘most’ will be used and the article ‘the’ always follows a superlative degree ‘most’. Here, ‘more’ will not come as it is used while comparing two things or people, etc. The correct sentence- I have presented with the most expensive dress on my birthday. Additional Information Mostly, we use the article ‘the’ before superlative degree but in some cases, the comparative degree also takes ‘the’ when there is a comparison and one is superior to others. For E.g. Shyam is the better of the two brothers.