Who wrote the important Indian English novel "Untouchable", which deals with the life of a sweeper boy in a single day?

Introduction / Context:
This question focuses on a foundational work of Indian English fiction. "Untouchable" is a novel that highlights the harsh realities of caste discrimination through the experiences of a sweeper boy over the course of a single day. It is widely discussed in literature courses and is important for questions on Indian social reform and English writing.

Given Data / Assumptions:

• The title "Untouchable" is given as an Indian English novel.
• Possible authors listed are Premchand, Sarojini Naidu, K. Natwar Singh and Mulk Raj Anand.
• Exactly one of these wrote the novel.

Concept / Approach:
Mulk Raj Anand is one of the early Indian English novelists who wrote about social injustice and the lives of the oppressed. "Untouchable" is perhaps his most famous work. Premchand wrote mainly in Hindi and Urdu, Sarojini Naidu was a poet, and K. Natwar Singh is known as a diplomat and writer of political works. Matching the theme of caste oppression and early Indian English prose with Mulk Raj Anand gives the correct answer.

Step-by-Step Solution:
Step 1: Recall that "Untouchable" portrays the life of Bakha, a sweeper boy, and his encounters with caste based humiliation. Step 2: This novel is a classic work by Mulk Raj Anand, who focused on social issues and the poor in his fiction. Step 3: Premchand is a major Indian writer but worked mostly in Hindi and Urdu with works like "Godaan". Step 4: Sarojini Naidu is recognised for her poetry and political leadership, not for this particular novel. Step 5: K. Natwar Singh is known for diplomatic and political writings rather than early social novels like "Untouchable". Step 6: Therefore, the correct answer is Mulk Raj Anand.

Verification / Alternative check:
Textbooks and histories of Indian English literature consistently identify Mulk Raj Anand as the author of "Untouchable". His name is closely tied to this novel when discussing caste issues and colonial era social criticism. You will not find credible sources attributing the work to Premchand, Sarojini Naidu or K. Natwar Singh, whose main contributions lie in different linguistic or literary areas.

Why Other Options Are Wrong:

• Premchand is wrong because although he dealt with similar social themes, he wrote in Hindi and Urdu and did not author this English novel.
• Sarojini Naidu is wrong because she is known more for poetry collections like "The Golden Threshold".
• K. Natwar Singh is wrong because his writings are mainly political memoirs and diplomatic accounts, not this kind of fictional narrative.

Common Pitfalls:
Candidates may associate any work dealing with Indian social problems with Premchand or confuse English and Hindi literature. Another mistake is to think of Sarojini Naidu as a novelist simply because she is a prominent literary name. Paying attention to the language and narrative form, and remembering that "Untouchable" is a landmark English novel by Mulk Raj Anand, will prevent such errors.

Final Answer:
The novel "Untouchable" was written by Mulk Raj Anand.