Which of the following features allows an operating system to access multiple virtual processors?

Hyper-threading (Intel HT Technology) uses simultaneous multithreading to expose multiple logical processors per physical core. The operating system sees and schedules threads across these virtual processors, enabling better utilization of a single core's execution units.

An integrated GPU handles graphics processing and does not create or expose virtual processors to the OS scheduler.

L2 cache is a memory cache that reduces latency when accessing frequently used data; it does not create additional logical processors.

Multiple cores provide additional physical processors, not virtual ones; hyper-threading is specifically the technology that creates virtual (logical) processors from a single physical core.