A security administrator is working to find a cost-effective solution to implement certificates for a large number of domains and subdomains owned by the company. Which of the following types of certificates should the administrator implement?

A wildcard certificate is the most cost-effective solution for securing a large number of domains and subdomains because it can secure a primary domain and an unlimited number of its subdomains with a single certificate (e.g., .example.com would secure example.com, www.example.com, mail.example.com, etc.). This eliminates the need to purchase individual certificates for each subdomain, significantly reducing costs and administrative overhead. Client certificates are used for authenticating users or devices, not for securing websites. Self-signed certificates are free but are not trusted by browsers and would generate security warnings for users, making them unsuitable for public-facing websites. Code signing certificates are used to verify the integrity and authenticity of software, not for securing web traffic.