Maasthi Venkatesa Iyengar (6 June 1891 – 6 June 1986) was a well-known writer in Kannada language. He was the fourth among Kannada writers to be honored with the Jnanpith Award, the highest literary honor conferred in India. He was popularly referred to as Maasti Kannadada Aasti which means "Maasti, Kannada's Treasure". He is most renowned for his short stories. He wrote under the pen name Srinivasa. He was honoured with the title Rajasevasakta by then Maharaja of Mysore Nalvadi Krishnaraja Wadeyar.

Answer:
Dr. Masti Venkatesh Iyengar was a renowned writer who made significant contributions to the field of literature. He primarily wrote in the Kannada language, which is spoken in the state of Karnataka in India. Here is a detailed explanation of why the correct answer is option D: Kannada.
Kannada Language:
- Kannada is one of the major Dravidian languages and is primarily spoken in the state of Karnataka.
- It has a rich literary tradition and is widely used for literature, poetry, and other forms of creative expression.
- Dr. Masti Venkatesh Iyengar was a prolific writer in Kannada and played a crucial role in shaping Kannada literature.
Contributions of Dr. Masti Venkatesh Iyengar:
- Dr. Masti Venkatesh Iyengar was a versatile writer and contributed to various genres of literature, including novels, short stories, plays, and essays.
- His works often depicted social issues, human emotions, and the struggles of individuals in a changing society.
- He received several prestigious awards for his writings, including the Jnanpith Award, which is one of the highest literary honors in India.
Conclusion:
In conclusion, Dr. Masti Venkatesh Iyengar wrote in the Kannada language. His literary works have left a lasting impact on Kannada literature and continue to be celebrated by readers and scholars alike.

Dr. Masti Venkatesh Iyengar's Language of Writing
Dr. Masti Venkatesh Iyengar was a renowned Indian writer who primarily wrote in the Kannada language. Known for his literary works, he made significant contributions to Kannada literature and was a prominent figure in the literary world.

Significance of Kannada Language
Kannada is one of the major Dravidian languages spoken predominantly in the state of Karnataka, India. It has a rich literary heritage and a long history of literary works, making it an important language in the cultural landscape of India.

Dr. Masti Venkatesh Iyengar's Works
Dr. Masti Venkatesh Iyengar wrote various novels, short stories, and essays in Kannada, which garnered him widespread acclaim and recognition. His works often depicted social issues, human emotions, and the cultural ethos of Karnataka.

Legacy in Kannada Literature
Dr. Masti Venkatesh Iyengar's literary contributions have had a lasting impact on Kannada literature, influencing generations of writers and readers. His works continue to be celebrated for their depth, insight, and literary merit.

Conclusion
In conclusion, Dr. Masti Venkatesh Iyengar was a prominent writer who wrote in the Kannada language, leaving behind a rich legacy in the realm of Kannada literature. His works remain an integral part of the literary canon in Karnataka and continue to inspire and resonate with readers.