Correct Answer: CThe most significant business risk to a company signing a contract with a CSP offering markedly reduced costs would be a control plane breach. This involves the compromise of the control plane, which is responsible for managing the cloud infrastructure, including operations like deploying, scaling, and managing virtual resources. A breach in the control plane can result in unauthorized access to sensitive data, service disruptions, and potential loss of control over the infrastructure. Given that the CSP is offering reduced costs, there might be concerns about the adequacy of their security measures, making this risk particularly significant.