Which statement best contrasts virtual machines and containers regarding isolation and overhead?

• A. Containers share the host kernel, offering lighter isolation.
• B. VMs use separate kernels; containers share the host kernel.
• C. VMs have lower overhead than containers.
• D. Containers are hardware virtualized.

Answer: (B)

The main idea is how isolation and resource cost differ because of kernel usage. Virtual machines provide strong isolation by running a full guest OS with its own kernel inside a hypervisor. Each VM has its own kernel, memory map, drivers, and system services, which makes them incrementally heavier to start and consume more resources. Containers, on the other hand, share the host’s kernel and isolate applications through namespaces and control groups, so there’s no separate kernel for each container. This leads to lighter isolation boundaries and much lower overhead, since you skip booting a full OS and duplicating kernel state.

The statement that best contrasts these aspects succinctly is that virtual machines use separate kernels while containers share the host kernel. It directly captures the mechanism behind the stronger isolation and the higher overhead of VMs versus the lighter, more efficient nature of containers.

Other options either describe containers’ sharing of the host kernel without acknowledging the VM kernel boundary, claim the opposite about overhead, or misstate how virtualization works (for example, containers being hardware virtualized is not correct).