Cost-reimbursement contracts are most commonly used for government-funded research projects with universities and non-profits because the costs and outcomes of such work are inherently uncertain. This contract type allows the government to reimburse the contractor for all allowable, allocable, and reasonable costs incurred during performance. It mitigates the financial risk for the research institution, which may lack the resources to absorb potential cost overruns associated with a fixed-price contract. This structure is ideal for research and development (R&D) where the primary goal is advancing knowledge rather than delivering a pre-defined product, making it the standard approach under federal acquisition regulations.

A. Written contracts: This is too general. While government contracts are written, this describes the form, not the specific pricing structure or type used for research.

B. Variable contracts: This is not a standard classification for government contract types. The term is ambiguous and not used in official procurement regulations.

D. Cost sharing contracts: Cost sharing is a feature, not a primary contract type. It is an arrangement, often included within a cost-reimbursement contract, where the contractor agrees to bear a portion of the project costs.

1. U.S. Federal Acquisition Regulation (FAR), Subpart 16.3, "Cost-Reimbursement Contracts." Section 16.301-2, "Application," states, "Cost-reimbursement contracts are suitable for use only when uncertainties involved in contract performance do not permit costs to be estimated with sufficient accuracy to use any type of fixed-price contract. A cost-reimbursement contract may be used only when... (b) The contract is for research and development..."

2. U.S. Federal Acquisition Regulation (FAR), Part 35, "Research and Development Contracting." Section 35.006(b) states, "The nature of R&D calls for a contract type that provides the contractor the maximum incentive for efficient and economic performance. The use of a cost-reimbursement contract is usually appropriate for R&D contracts."

3. National Contract Management Association (NCMA), Contract Management Body of Knowledge (CMBOK), 6th ed. Competency 2.1.2, "Select Contract Type." The CMBOK explains that cost-reimbursement contracts are appropriate when cost uncertainties are high, a condition characteristic of research and development efforts undertaken by universities and non-profits.

4. University of California, Office of the President, "Contract and Grant Manual," Chapter 13-210, "Cost Reimbursement." The manual states, "Cost reimbursement awards are the most common award mechanism for research. Under a cost reimbursement award, the sponsor agrees to pay for all allowable costs incurred in the conduct of the project up to a stated maximum."