B. True Containers are indeed highly portable code execution environments. Containers provide a lightweight and isolated runtime environment that encapsulates an application and its dependencies. This allows the containerized application to run consistently and reliably across different computing environments, such as development machines, testing environments, and production servers. Containers achieve portability by bundling the application code, runtime dependencies, libraries, and configuration files into a single package. This package, known as a container image, can be easily distributed and deployed on various host systems that have a compatible container runtime, such as Docker or Kubernetes. Containers abstract away the underlying infrastructure and operating system differences, making it possible to run the same containerized application consistently across different environments.

As stated in Security-Guidance-v4.0, Pg 85, "Containers are code execution environments that run within an operating system (for now), sharing and leveraging resources of that operating system" They are designed to be highly portable and can run on different operating systems and cloud platforms. Thus, the statement is True.