Explanation:

- Kavita's work rate is 1/12 of the work per hour.

- Komal's work rate is 1/18 of the work per hour.

- Kavita works alone for 4 hours, completing $\frac{4}{12}=\frac{1}{3}$ of the work.

- Thus, $\frac{2}{3}$ of the work is still left.

- Komal needs to complete the remaining $\frac{2}{3}$ of the work.

- Time taken by Komal to finish this is $\frac{2/3}{1/18}=12$ hours.

- Correct Answer: Komal takes 12 hours to finish the remaining work.