-  use has

The sentence is a negative statement that uses the conjunction "neither" to express that both Rohit and Kabir have not done their lesson. However, the use of "his" in Part 3 is incorrect, as it is a singular pronoun and cannot be used to refer to two subjects.

To correct this error, we need to use a plural pronoun to refer to both Rohit and Kabir. The correct pronoun is "their," which is a plural possessive pronoun that can be used to refer to two or more people.

Here are some relevant definitions and formulas related to this topic:

• Pronoun: A pronoun is a word that takes the place of a noun in a sentence. It can be used to avoid repetition and make sentences shorter and clearer.
• Singular pronoun: A singular pronoun is a pronoun that refers to one person, animal, or thing. Examples include "he," "she," "it," and "his."
• Plural pronoun: A plural pronoun is a pronoun that refers to two or more people, animals, or things. Examples include "they," "we," "you," and "their."
• Possessive pronoun: A possessive pronoun is a pronoun that shows ownership or possession. Examples include "his," "hers," "theirs," and "its."

In conclusion, the correct answer is option C, as Part 3 contains a grammatical error that needs to be corrected by replacing "his" with "their."