Indefinite-delivery contracts cover which of the following?

Indefinite-delivery contracts are designed to provide for an ongoing supply of goods or services without a specified quantity or timeframe, and they encompass a variety of contract types. This makes the answer that covers "all types of contracts" the most accurate choice.

These contracts can include fixed-price, cost-reimbursement, and time-and-materials contracts, allowing for flexibility in procurement to meet the needs of the government agency. This flexibility is essential for accommodating uncertain requirements that may arise over a period of time, allowing for streamlined and efficient acquisition.

The scope of indefinite-delivery contracts aims to provide purchasers with the ability to engage in multiple deliveries or performance over time while maintaining contract terms that can adapt to changing circumstances or demand. Other options focus too narrowly on specific types of contracts or agreements, which do not reflect the full capability and purpose of indefinite-delivery contracts.