Mutual TLS (mTLS) is the core mechanism for securing service-to-service communication in cloud native environments. Option B is correct because mTLS provides encryption in transit and mutual authentication, ensuring both the client and server verify each other’s identity. This prevents unauthorized access, man-in-the-middle attacks, and data leakage.

Option A (API Gateway) manages ingress traffic from external clients but does not secure internal service-to-service communication. Option C (Service Mesh) is a broader infrastructure layer (e.g., Istio, Linkerd) that implements mTLS, but mTLS itself is the mechanism that enforces secure communications. Option D (Load Balancer) distributes traffic but does not handle encryption or authentication.

mTLS is foundational to zero-trust networking inside Kubernetes clusters. Service meshes typically provide automated certificate management and policy enforcement, ensuring seamless adoption of mTLS without requiring developers to modify application code.