The ‘Posa’ system practiced by some tribes involved:

The correct answer is: a) Collection of tributes from neighboring villages.

The ‘Posa’ system is a traditional system of taxation practiced by some tribes in the Philippines. Under this system, villages are required to pay a tribute to the ruling tribe. The tribute is usually paid in the form of rice, livestock, or other goods. The purpose of the ‘Posa’ system is to provide the ruling tribe with a source of income and to ensure their political and economic dominance over the other villages.

The other options are incorrect because:

• Option b) is incorrect because communal land ownership is a system in which land is owned and managed by a community as a whole, rather than by individuals.
• Option c) is incorrect because ritual sacrifices are not a part of the ‘Posa’ system.
• Option d) is incorrect because barter trade is a system of exchange in which goods or services are directly exchanged for other goods or services, without the use of money.