The correct answer is option 'D', clergy and nobility.

The privileged class in the context of this question refers to the social groups that held special privileges and advantages in society. These privileges often included exemptions from certain taxes, control over important positions and resources, and a higher social status. In the pre-modern era, the privileged class was typically made up of the clergy and nobility.

Let's break down the options and understand why 'clergy and nobility' is the correct answer.

a) Clergy and peasants:
- The clergy refers to the religious officials, such as priests, bishops, and monks.
- Peasants, on the other hand, were the common people who worked in agriculture.
- While the clergy did have certain privileges and exemptions due to their religious role, they were not part of the privileged class as a whole. They did not hold the same level of political and social power as the nobility.

b) Peasants and nobility:
- As mentioned earlier, peasants were the common people who worked in agriculture.
- The nobility, on the other hand, comprised the highest social class in the feudal system. They held titles such as kings, queens, dukes, and lords and owned vast amounts of land.
- While the nobility did indeed belong to the privileged class, peasants did not. Peasants were usually subjected to harsh conditions, heavy taxation, and limited freedoms.

c) First and Third Estates:
- The First Estate referred to the clergy, while the Third Estate represented the commoners, including peasants, artisans, and the bourgeoisie.
- The Second Estate, which comprised the nobility, is missing from this option.
- While the First Estate (clergy) and the Third Estate (commoners) played crucial roles in society, it is the combination of the clergy and nobility that constituted the privileged class.

d) Clergy and nobility:
- This option correctly identifies the two social groups that made up the privileged class.
- The clergy, as mentioned earlier, consisted of religious officials who held considerable power and influence.
- The nobility, as the highest social class, possessed significant political, economic, and social privileges.

In conclusion, the correct answer is option 'D', clergy and nobility, as they were the two social groups that constituted the privileged class in pre-modern societies.