Introduction:
Federalism is a system of governance in which power is divided between a central authority and various regional units. It allows for the coexistence of a strong central government along with local governments, each having their own powers and responsibilities. In the given options, Pakistan, Russia, and Brazil are the countries that practice federalism.

1. Pakistan:
- Pakistan practices federalism with a central government and four provinces (Punjab, Sindh, Khyber Pakhtunkhwa, and Balochistan) having their own legislative and executive bodies.
- Each province has the power to make laws and regulations on various subjects assigned to them by the constitution.
- The central government has authority over subjects such as defense, foreign affairs, currency, and communication.

2. Russia:
- Russia follows a federal system with a central government and 85 federal subjects, which include republics, regions, territories, and federal cities.
- The federal subjects have their own constitutions, presidents, and legislatures, which have the power to make laws on various matters.
- However, the central government holds significant power, especially in defense, foreign policy, and economy.

3. Brazil:
- Brazil is a federal republic composed of the federal government and 26 states, along with one federal district.
- Each state has its own constitution, governor, and legislature, which have the authority to legislate on state matters.
- The central government has powers in areas such as defense, foreign affairs, and currency.

Conclusion:
In conclusion, Pakistan, Russia, and Brazil practice federalism. Each of these countries has a central government and regional units with varying degrees of autonomy and powers. While the central government retains authority over certain key areas, the regional units have the power to legislate and govern on matters assigned to them. Therefore, the correct answer is option 'D' - All of the above.