When we're reporting a speech, we're narrating things that happened or were said in the past. So, the speech will go one tense back.

In reported speech, we add a reporting verb (usually 'said'), the subject changes in narration ('he', 'she' or 'they') and the related words also change.

Option B: For reporting the speech of the Exhibitor, 'this' changes to 'that'. 'Is' is in the simple present, it changes to 'was', the simple past verb.

So, the corrected reported speech for the sentence "No ma'am. This vase is not for sale." is:

'The Exhibitor answered in the negative and informed the lady that that vase was not for sale.' (The first 'that' is a relative pronoun and introduces the speech, the second 'that' refers to 'this vase'.)

The words 'No, ma'am'' are both in direct format and there is no indirect form other than 'answered in the negative'.

Hence option B is correct.

Option A: The word 'rudely' does not describe the manner in which the exhibitor spoke. It does not mean the same as 'No, ma'am'.

Option C: The word 'this' hasn't been changed here.

Option D: 'This' has not been changed to 'that', and the verb 'is' has also not been changed.