The Battle of Buxar was fought for a combination of reasons, but the correct answer is option 2: Mir Kasim joined hands with Shah Alam II and Shuja-ud-daulah against the English.

To understand this answer, let`s break down the other options:

- Option 1 states that Shah Alam II wanted to chastise the Nawab of Oudh and Nawab of Bengal. While there were tensions among these rulers, it was not the main reason for the Battle of Buxar.

- Option 3 suggests that the Marathas wanted to expel the English from Oudh and free Shah Alam II from confinement. While the Marathas did have ambitions to limit English influence, their involvement in the Battle of Buxar was limited.

- Option 4 states that Shuja-ud-daulah wanted the help of Mir Kasim and the English to be saved from the Marathas. This is not a reason for the Battle of Buxar, as Shuja-ud-daulah`s alliance with Mir Kasim and Shah Alam II was directed against the English.

Therefore, option 2 is correct. Mir Kasim, in an effort to resist English domination, teamed up with Shah Alam II and Sh