Hello,
The answer is option A "moving onto American Indian lands".
Reason:
The answer is option A because indentured servants who usually were freed cause conflict by moving on Indian territory. Its also not option B because plantations are mainly where slave works. Its also not option C because indentured slaves wouldn't by more slaves because Africans were not allowed o do that at the certain point of time. Its also not D because Jamestown was built by colonists.
If you need anymore help feel free to ask me!
Hope this helps!
~Nonportrit