Final answer:
The correct AWS service for protecting network- and host-level boundaries is not explicitly mentioned in the options, but Amazon Web Services (AWS) itself offers services like AWS Shield, AWS WAF, and Amazon VPC for such tasks.
Step-by-step explanation:
The key AWS service that supports the protection of network- and host-level boundaries in infrastructure protection is not listed among the options provided. However, the correct AWS service for this task would typically be Amazon Web Services (AWS) itself, more specifically services such as AWS Shield for DDoS protection, AWS WAF (Web Application Firewall) for protecting web applications, or more foundational services like Amazon VPC (Virtual Private Cloud) for network isolation. Services like Amazon Prime, Amazon Fresh, and Amazon Alexa are unrelated to infrastructure protection in the context of cloud computing.
If we look at the given options in the context of AWS infrastructure protection, option b) Amazon Web Services (AWS) is the only relevant option, though it's a broad term that encompasses several specific services for network and host protection.