单选题：根据以下资料，回答题：Slavery has played a significant role in the his

根据以下资料，回答题：
Slavery has played a significant role in the history of the U．S．It existed in all the English mainland colonies and most of the Founding Fathers also had slaves，as did eight of the first l2 presidents．
Dutch traders brought，20 Africans to Jamestown，Virginia，as early as l619，however，throughout the l7th century the number of Africans in the English mainland colonies grew very slowly．At that time，colonists used two other sources of unfree labor：Native American slaves and European indentured servants．
During those years，every colony had some Native American slaves，but their number was limited．Indian men avoided performing agricultural labor，because they viewed it as women’s work，and colonists complained that they were t00“haughty”．The more important was that the settlers found it more convenient，to sell Native Americans captured in war to planters in the Carib—bean than to turn them into slaves，because they often resisted and it was not hard for the slaves to escape．Later，the policy of killing Indians or driving them away from white settlements was pro-posed and it contradicted with their widespread employment as slaves．
The other form of labor was the white indentured servitude．Most indentured servants consisted of poor Europeans．Desiring to escape tough conditions in Europe and take advantage of fabled op—portunities in America，they traded three to seven years of their labor in exchange for the transatlan—tic passage．At first，it was mainly English who were the white indentured servitude but later in—creasingly Irish，Welsh，and German joined．They were essentially temporary slaves and most of them served as agricultural workers although some，especially in the North，were taught skilled trades．During the l 7th century，they performed most of heavy labor in the Southern colonies and also consisted of the bulk of immigrants to those colonies．
At the end of the l7th century．in order to meet the labor need，landowners in America turned to African slaves．During the late l7th and l8th centuries，thanks to the dominant position of Eng—land in terms of naval superiority，English traders(some of whom lived in English America)，trans-ported millions of Africans across the Atlantic．And the transatlantic slave trade produced one of the largest forced migrations in history, blacks(the great majority of whom were slaves)。increasing from about 7 percent of the American population in l680 to more than 40 percent by the middle of the l8th century．

Which of the following was true of the slavery in America? A．The colonists sold African Americans to planters in the Caribbean．
B．Native American slaves performed agricultural labor．
C．During the l7th century，the white indentured servitude was the main labor in the Southern colonies．
D．It was at the end of the l7th century that African people began to be brought to A-merica.