Explanation:
When it comes to transferring bulk data from a hard disk drive (HDD) to main memory, the most efficient method is DMA (Direct Memory Access) based I/O transfer. DMA is a technique that allows peripheral devices, like the HDD, to transfer data directly to and from main memory without involving the CPU.

Programmed I/O transfer:
- In programmed I/O transfer, the CPU is responsible for performing all the data transfers between the HDD and main memory.
- The CPU issues read or write commands to the HDD and waits for the transfer to complete.
- This method requires constant intervention from the CPU, which leads to a significant overhead and reduces the overall throughput.
- In the case of transferring bulk data, this method would result in low throughput and inefficient utilization of the CPU.

Interrupt driven I/O transfer:
- In interrupt driven I/O transfer, the CPU issues a read or write command to the HDD and continues with other tasks.
- When the transfer is complete, the HDD raises an interrupt signal to inform the CPU.
- The CPU then suspends its current task, handles the interrupt, and performs the necessary data transfer between the HDD and main memory.
- While this method reduces the CPU overhead compared to programmed I/O transfer, it still requires the CPU to be involved in each transfer.
- Therefore, it is not the most efficient method for transferring bulk data.

Polling based I/O transfer:
- In polling based I/O transfer, the CPU periodically checks the status of the HDD to determine if the transfer is complete.
- This method also requires constant intervention from the CPU, similar to programmed I/O transfer.
- It suffers from the same overhead and reduced throughput when it comes to transferring bulk data.

DMA based I/O transfer:
- DMA allows the HDD to transfer data directly to and from main memory without involving the CPU.
- The CPU sets up the DMA controller with the necessary information, such as the source and destination addresses, and the transfer size.
- Once the DMA controller is configured, it takes control of the data transfer process and performs the transfer independently of the CPU.
- This method significantly reduces the CPU overhead and improves the overall throughput, especially when transferring bulk data.
- The CPU can continue executing other tasks while the DMA controller handles the data transfer, resulting in efficient utilization of system resources.

Therefore, the DMA based I/O transfer facilitates the transfer of bulk data from the HDD to main memory with the highest throughput.