The correct option is "B. Brazil became an independent kingdom under the Portuguese royal family."
The Kingdom of Brazil is the name given to the State by the arrival of the Portuguese royal family and its Court, after the Napoleonic occupation of Portugal in 1808 which, once liberated, officially unite on December 16, 1815 as the United Kingdom. Portugal, Brazil and Algarve.
The prince of Brazil and regent of the Kingdom of Portugal in exile, Juan VI, would assume the Luso-Brazilian throne on March 20, 1816, for the death of the sick queen María I of Portugal, and although he began to govern as king formal, his effective coronation had to wait until February 6, 1818.
The continuity of this Luso-Brazilian kingdom has been the Empire of Brazil and, currently, the homonymous Federal Republic.