Which of These Best Explains the Fact That Early-Seventeenth-Century Virginia

Which of these best explains the fact that early-seventeenth-century Virginia planters employed far more indentured servants than slaves?

A) Slaves generally cost twice as much as indentured servants.
B) Planters preferred to work with other European Christians.
C) Planters had no way to gain access to an adequate supply of slaves.
D) Slaves were seen as poor workers.