When their period of service ended, indentured servants

Were needed as workers on plantations, is the right answer.

Explanation:

Indentured servants exist throughout the colonial era in Virginia. It loaded with a community who determined to confirm a work contract in return for passage to Virginia along with some basic amenities such as food clothing and shelters. However, when they were left with nothing they had no choice but to sign the contract as a plantation worker once again.