B. The correct answer is PC2-6400. This is a type of DDR2 memory module that can transfer 6,400 MBps. It is based on the DDR2-800 standard. PC2-5300 can only transfer 5,333 MBps; that is known as the DDR2-667 standard. PC3-6400 does transfer 6,400 MBps, but it is a DDR3 standard known as DDR3-800. DDR3 modules cannot be installed into DDR2 memory slots. DDR2-667 once again is a DDR2 standard that specifies 5,333 MBps data transfer.