Correct Answer: CTo achieve the objective of discovering SaaS applications and blocking access to unapproved or risky ones for a highly distributed remote workforce, the most effective solution would be to implement cloud infrastructure to proxy all user web traffic and control access according to a centralized policy. This approach does not require deploying endpoint agents which can be challenging to manage across a distributed workforce. Instead, it ensures that all user web traffic is routed through a central proxy, allowing for consistent enforcement of security policies, discovery of SaaS applications, and the ability to block access to unapproved or risky applications in a scalable and efficient manner.