The correct answer is: D. On-chip paging memory management unit
An on-chip paging memory management unit (MMU) is a hardware device that is used to manage the memory of a computer. It does this by dividing the memory into pages, and then keeping track of which pages are being used by which processes. This allows the MMU to quickly and efficiently switch between processes, which is essential for multitasking.
The other options are incorrect because they do not support multitasking. Read mode is a mode of operation for the 80386 processor that allows it to read data from memory. External paging memory management unit is a type of MMU that is located outside of the processor. Paging and segmentation are two techniques that are used to manage memory in the 80386 processor, but they do not support multitasking on their own.
In conclusion, the on-chip paging memory management unit is the only option that supports multitasking in the 80386 processor.