What are two likely causes for a DRS cluster to become unbalanced? (Choose two.)

A conservative (low) migration threshold reduces the frequency and priority of DRS recommendations but does not create an absolute migration block - it simply raises the imbalance severity required before a recommendation is issued.

VM-to-VM or VM-to-host affinity and anti-affinity rules can prevent DRS from issuing valid migration recommendations for specific VMs, leaving those VMs pinned to overloaded or underutilized hosts and causing a sustained imbalance in the cluster.

A locally attached device such as a connected CD-ROM, floppy, or USB passthrough device renders a VM ineligible for vMotion, so DRS cannot migrate it to rebalance load even when a significant imbalance exists.

Migration cost is an internal DRS calculation factor used to weigh the benefit of a migration against its overhead - it is not a standalone administrator-configurable setting and a low migration cost would encourage more migrations rather than prevent rebalancing.