To answer this question, the user must have knowledge of the life of Mahatma Gandhi.

Gandhiji's father's name was Karamchand Uttamchand Gandhi. He was a prominent figure in Porbandar, an Indian city in Gujarat.

Now, let's review each option to determine which one is correct:

A. Farmer: This option is incorrect. Although farming was a common occupation in Gandhi's native Gujarat, his father was not a farmer.

B. Diwan: This option is correct. Karamchand Uttamchand Gandhi was a diwan, a high-ranking official who served as a chief minister of Porbandar and later Rajkot.

C. Shopkeeper: This option is incorrect. Although some of Gandhi's relatives were shopkeepers, his father was not.

D. Tehsildar: This option is incorrect. A tehsildar is a revenue officer in India, which was not the profession of Gandhi's father.

Therefore, The Answer is: B. Diwan.