You are developing a new ecommerce application that uses Cloud Functions. You want to expose your application's APIs to public users while maintaining a high level of security. You need to ensure that only authorized users can access your APIs and that all API traffic is encrypted and protected from unauthorized access. You want to use the most scalable and secure approach. What should you do?

A. Deploy your Cloud Functions behind Cloud Load Balancing, and use Cloud Armor to protect your APIs from distributed denial of service (DDoS) attacks. B. Deploy your Cloud Functions with Security Command Center enabled, and use IAM to manage access to your APIs. C. Deploy your Cloud Functions behind an Apigee proxy and use Apigee’s authentication and authorization features to secure your APIs. D. Deploy your Cloud Functions behind a Cloud API Gateway proxy. Create and use an API key to authorize users to access your APIs.