The most secure action an administrator can take to protect the company from unauthorized access to NetSuite data is to use Two-Factor Authentication (2FA). 2FA adds an additional layer of security by requiring users to provide two forms of identification before gaining access to the system. The first factor is something the user knows (like a password), and the second factor is something the user has (such as a mobile device for receiving a verification code). This method significantly reduces the risk of unauthorized access because even if a password is compromised, without the second form of verification, access is not granted. Setting the NetSuite Password Policy to Strong (Option A) and requiring password changes every few days (Option B) are good practices but don't provide the same level of security enhancement as 2FA. Requiring users to answer security questions upon login (Option C) adds a layer of security but is still based on knowledge factors and can be less secure than a possession factor used in 2FA.References: NetSuite Security Practices and Documentation.