An engineer must implement a public cloud solution that enables a company to place all...

Comprehensive and Detailed Explanation (Cisco Cloud Model Knowledge)

The requirement states:

All infrastructure in the cloud

All applications delivered from the cloud

No software management

No maintenance by the customer

This matchesSoftware as a Service (SaaS).

SaaS provides:

Fully managed applications

No patching, upkeep, installation, or infrastructure maintenance

End-to-end cloud delivery

PaaS and IaaS still require some software/application management.

FaaS is event-driven serverless compute, not full application hosting.

Therefore, the correct answer isA. SaaS.