Final answer:
He spoke out against the brutality and mistreatment of Native Americans in his book 'A Short Account of the Destruction of the Indies'.The correct option is A.
Step-by-step explanation:
The primary Spanish critic of the Spanish system of conquering and encomienda is Bartolomé de las Casas.
He was a Dominican friar who traveled across Latin America and Spain, speaking out against the brutality of the system.
In his book, 'A Short Account of the Destruction of the Indies', Las Casas argued against the violence and mistreatment of Native Americans by the Spanish. The correct option is A.