Explanation:

The Fifteenth Finance Commission (XV-FC) made several changes to the criteria for horizontal tax devolution.

Out of the provided options, the criteria used by the XV-FC for horizontal tax devolution were:

Demographic Performance: To reward efforts in population control.

Forest and Ecology: This was used to address the inter-state disparity in sharing public expenditure responsibilities.

Tax and fiscal efforts: To reward fiscal management.

The other main criteria used by the XV-FC were population data from both 1971 and 2011, area, and income distance.

Hence, Governance reforms and Stable government were not used as criteria by the XV-FC for horizontal tax devolution.

The correct answer is:

2. Only three.