With kubeadm at v1.35, how far behind may the kubelet on a host be?

Answer: C. Three minor versions

kubeadm supports a kubelet at its own version or up to three minor versions older, a wider skew than it allows for the control plane components it deploys.

Source: Creating a cluster with kubeadm (Kubernetes) — Version skew policy › kubeadm's skew against the kubelet