Introduction:
The correct answer to the question is option 'D' - Sundays. This means that the person used to write novels on Sundays. Let's explore the reasons and details behind this answer.

Explanation:
- Writing novels requires time, concentration, and creativity. It is a process that requires uninterrupted focus and dedication.
- Many writers develop a routine or schedule to ensure regular writing sessions and maintain productivity.
- The person mentioned in the question used to write novels on Sundays, which implies that they dedicated a specific day of the week to their writing practice.

Reasons for choosing Sundays:
1. Time availability: Sundays are typically considered a day off from work or other commitments. This means that the person has more free time available to dedicate to their writing without distractions.
2. Mental and physical relaxation: After a week of work or other activities, people often use Sundays as a day to relax and recharge. This mental and physical relaxation can enhance creativity and focus during the writing process.
3. Consistency and routine: By choosing a specific day of the week for writing novels, the person establishes a routine and ensures regularity in their writing practice. Consistency is a key factor in developing and honing writing skills.
4. Minimal interruptions: Sundays are often associated with a slower pace of life compared to weekdays. There are typically fewer external interruptions such as work-related commitments, social events, or household chores. This allows the person to fully immerse themselves in the writing process.

Conclusion:
In conclusion, the person in question used to write novels on Sundays. By dedicating a specific day of the week to their writing practice, they were able to ensure regularity, consistency, and minimal interruptions. Writing on Sundays provided them with the necessary time, relaxation, and focus to pursue their creative endeavors.