Which of the following can be considered as a type of memory module?

The designation of DDR as a type of memory module is accurate because DDR stands for Double Data Rate. It is an advanced type of synchronous dynamic random-access memory (SDRAM) that transfers data on both the rising and falling edges of the clock cycle, thereby doubling the effective bandwidth compared to conventional SDRAM. DDR memory modules are widely used in computers and are critical in enhancing performance because they allow for faster data transfer rates, which is essential for modern applications that require quick access to large amounts of data.

In contrast, other options do not fit the category of memory modules. SDRAM is indeed a type of memory, but it is more of a general category that encompasses various types of memory, including DDR itself. PCI Express is a high-speed interface standard used for connecting peripherals like graphics cards and is not a memory type. Flash Memory, while it serves as storage and can be used in devices like SSDs, does not qualify as a memory module in the same context as DDR. Thus, DDR stands out clearly as the specific type of memory module among the given options.