Improvement of the bracketed part:

The correct improvement for the bracketed part of the sentence is option 'B': "doesnt he."

Explanation:

The original sentence is: "Virat bats very well, (didnt he)?"

In this sentence, the speaker is expressing their belief that Virat bats very well. To make it a question, we need to use the appropriate tag question at the end. A tag question is a short question added at the end of a sentence to confirm or check information.

Tag questions:
Tag questions are formed by using an auxiliary verb that matches the tense and subject of the main part of the sentence. In this case, the main part of the sentence is "Virat bats very well," which is in the present tense and affirmative form. Therefore, the tag question should be in the present tense and negative form.

Option 'A': "isnt it"
This option uses the present tense and negative form of "is" as the auxiliary verb. However, "isn't it" is used when the main part of the sentence is in the first or second person (I, you, we, they). In this case, the main part of the sentence is about Virat, so "isn't it" is not appropriate.

Option 'B': "doesnt he"
This option uses the present tense and negative form of "do" as the auxiliary verb. "Doesn't he" is the correct tag question to use in this case. It matches the present tense and negative form of the main part of the sentence ("Virat bats very well").

Option 'C': "wasnt it"
This option uses the past tense and negative form of "be" as the auxiliary verb. However, the main part of the sentence is in the present tense, so using the past tense is not appropriate.

Option 'D': no improvement
This option suggests that the original sentence is already correct and does not need any improvement. However, as mentioned earlier, the original sentence needs a tag question to make it a question.

Therefore, the correct improvement for the bracketed part of the sentence is option 'B': "doesnt he," which forms a correct tag question to match the present tense and negative form of the main part of the sentence.