ANSWER: A) DMA based I/O transfer
In DMA (Direct Memory Access) mode, bulk amount of data is transferred from IO Device to Main Memory without the involvement of CPU. Whenever Prg Size > MM size, Virtual Memory is used with the help of Secondary Memory. Secondary memory is interfaced to system via DMA Module.
So why highest throughput?
This way, the CPU can keep working on other tasks while all the data is being moved. Think as if DMA is a super-fast moving truck that can transfer huge amounts of data from the hard drive to the computer's memory without needing the CPU to help it out. And because it can move more data in a shorter amount of time, it's like getting a lot more done in a shorter amount of time, that's why we call the “highest throughput” among other methods.