KCNA Container Orchestration Practice Question
Which THREE of the following are true about the Container Runtime Interface (CRI)? (Choose 3)
⚠ Common exam trap
KCNA often tests the misconception that Docker is a CRI runtime or that CRI is an OCI standard — candidates must distinguish Kubernetes' CRI from OCI's image/runtime specs.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
CRI allows kubelet to communicate with different container runtimes
Option C is correct because the Container Runtime Interface is precisely the gRPC API that kubelet uses to talk to a container runtime, decoupling Kubernetes from any single runtime implementation. Option D is correct because containerd ships a built-in CRI plugin (enabled by default) that lets kubelet use containerd directly as a CRI-compliant runtime. Option E is correct because CRI-O is a lightweight OCI-compliant container runtime built specifically to serve as a Kubernetes CRI implementation. Option A is not correct because Docker does not natively implement CRI; the historical dockershim adapter was needed to bridge kubelet to Docker, and it has since been removed. Option B is not correct because CRI is a Kubernetes project specification, not part of the Open Container Initiative, which instead defines the OCI runtime and image specifications.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Docker natively implements the CRI
Why it's wrong here
Docker predates CRI and communicates with Kubernetes through the dockershim shim rather than implementing the CRI gRPC interface natively; containerd and CRI-O do. It is tempting because Docker is the best-known runtime, and it would be correct to say Docker uses a CRI-compliant runtime underneath.
- ✗
CRI is part of the Open Container Initiative (OCI)
Why it's wrong here
CRI is a Kubernetes specification defining the kubelet-to-runtime gRPC interface; OCI governs image format and runtime standards, a separate body. It is tempting because both concern container runtimes, and OCI membership would be the correct description of runc or containerd's image specification compliance.
- ✓
CRI allows kubelet to communicate with different container runtimes
Why this is correct
CRI is the abstraction layer between kubelet and container runtimes, defining gRPC services (RuntimeService, ImageService) so kubelet can drive containerd, CRI-O or others without runtime-specific code. This directly satisfies the stem's requirement that CRI enables kubelet to communicate with different container runtimes.
- ✓
containerd implements the CRI
Why this is correct
containerd is a CRI-compliant runtime, exposing the gRPC CRI service that kubelet calls to manage pods and containers. This satisfies the stem's requirement that the statement be true of CRI, since containerd natively implements the interface rather than relying on a shim such as dockershim.
- ✓
CRI-O is a lightweight runtime designed for Kubernetes
Why this is correct
CRI-O implements the Kubernetes Container Runtime Interface directly, so kubelet drives it without Docker's daemon layer. Its narrow, Kubernetes-only scope satisfies the stem's CRI constraint: it is a genuine CRI-compliant runtime, unlike Docker Engine, which required the deprecated dockershim adapter.
Go deeper
Related to this question
Learn chapter
Container Orchestration Essentials
Key term
Container Runtime Interface
The Container Runtime Interface (CRI) is a standardized plugin protocol that allows Kubernetes to work with different container runtimes without needing to change its core code.
Key term
ReplicaSet and Replication
A ReplicaSet ensures a specified number of identical pod instances are running at all times in Kubernetes, using replication to maintain availability and stability.
About these practice questions
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CNCF exam blueprint
This KCNA practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the KCNA exam.