The correct answer is option D: The growth of Devaraja cult.

Explanation:
The Chola period, which lasted from the 9th to the 13th century, witnessed an important development in the institution of monarchy. During this time, the Chola kings adopted the Devaraja cult, which played a significant role in shaping the nature of their rule.

1. The Devaraja Cult:
- The Devaraja cult was a religious and political ideology that portrayed the king as a divine ruler, representing a fusion of religious and political authority.
- According to this cult, the king was considered the earthly representative of the gods and was believed to possess divine attributes.
- The king was seen as the central figure in the religious and social life of the kingdom, with his actions and decisions being closely associated with religious rituals and beliefs.

2. The King as the Manifestation of God:
- The growth of the Devaraja cult resulted in the king being seen as the manifestation of a particular deity, usually Shiva or Vishnu.
- This belief enhanced the king's authority and legitimacy, as he was regarded as being chosen by the gods to rule.
- The king's association with a specific deity also helped in establishing a connection between the royal court and the temples, leading to the development of a close relationship between the king and the priesthood.

3. Rituals and Ceremonies:
- The adoption of the Devaraja cult led to the introduction of various rituals and ceremonies that emphasized the king's divine status.
- Elaborate coronation ceremonies were conducted to legitimize the king's rule and reinforce his association with the gods.
- The king's role in religious festivals and processions further enhanced his image as a divine ruler.

4. Patronage of Temples and Religious Institutions:
- As a result of the growth of the Devaraja cult, the Chola kings became great patrons of temples and religious institutions.
- They contributed to the construction and renovation of numerous temples, which served as centers of religious and cultural life.
- The kings also made generous donations to priests, scholars, and artists, further strengthening their ties with the religious community.

In conclusion, the growth of the Devaraja cult during the Chola period had a profound impact on the institution of monarchy. It elevated the status of the king to that of a divine ruler and shaped the nature of his rule, emphasizing the close association between religion and politics.