Explanation

AWS Certificate Manager (ACM) is the correct service for securing web applications with SSL/TLS encryption because:

• ACM provides SSL/TLS certificates that can be used to encrypt traffic between clients and web applications
• It automatically handles certificate provisioning, deployment, and renewal
• ACM certificates can be easily integrated with AWS services like Elastic Load Balancers, CloudFront distributions, and API Gateway
• The service is free when used with supported AWS services

Why other options are incorrect:

• AWS WAF: Web Application Firewall - protects against web exploits, not SSL/TLS encryption
• AWS Shield: DDoS protection service - protects against distributed denial of service attacks
• Amazon VPC: Virtual Private Cloud - provides network isolation and segmentation, not SSL/TLS encryption

ACM is specifically designed to simplify the process of obtaining, managing, and deploying SSL/TLS certificates for AWS workloads.