On the basis of ownership of enterprises, the sectors are classified into public and private sectors . Public sectors are the government owned sectors sectors whereas private sectors are not the government owned sectors. Private sectors are owned by the individuals or a group of individuals.

The classification of sectors into public and private sectors is based on the ownership of enterprises. Let's understand this in detail:

Ownership of Enterprises:
- In the public sector, the enterprises are owned and operated by the government or government bodies. These enterprises are funded by the government and are accountable to the public. Examples of public sector enterprises include government schools, hospitals, railways, etc.

- In the private sector, the enterprises are owned and operated by private individuals or organizations. These enterprises are funded by private investments and are accountable to their owners. Examples of private sector enterprises include private schools, hospitals, multinational companies, etc.

Explanation of Other Options:
a) Employment conditions: This option is not relevant to the classification of sectors into public and private sectors. Employment conditions can vary within both public and private sectors and are not a determining factor for classification.

b) The nature of economic activity: While the nature of economic activity can vary between sectors, it is not the basis for classifying sectors into public and private sectors. Both public and private sectors can engage in a wide range of economic activities.

c) Ownership of enterprises: This is the correct basis for classifying sectors into public and private sectors. It distinguishes between enterprises that are owned by the government (public sector) and those that are owned by private individuals or organizations (private sector).

d) Number of workers employed in the enterprise: The number of workers employed in an enterprise is not the basis for classifying sectors into public and private sectors. Both public and private sectors can have enterprises with varying numbers of workers.

In conclusion, the classification of sectors into public and private sectors is based on the ownership of enterprises. It distinguishes between enterprises owned by the government (public sector) and those owned by private individuals or organizations (private sector).