Users are reporting slow performance on a virtual server. An administrator notices that the virtual CPU is at 50%. Which of the following should the administrator check on the host?

I/O throttling is a disk or network I/O constraint mechanism and would affect storage or network performance, not CPU scheduling latency.

CPU wait time (also called CPU ready time in hypervisor platforms) measures how long a vCPU is ready to run but must wait for a physical CPU core to become available on the host. Even at 50% reported utilization, high CPU wait time indicates that the VM is being starved of physical CPU cycles by the hypervisor scheduler, directly causing the observed slow performance.

Swap files relate to memory overcommitment - when the host runs out of physical RAM and pages to disk - which is a memory issue, not a CPU scheduling problem.

Memory ballooning is a hypervisor technique to reclaim memory from VMs with low memory pressure, which is a memory management concern unrelated to CPU scheduling delays.