Which correctly explains why Rowhammer is said to become more likely as DRAM is scaled down?

Answer: B. Cells get closer together and store less charge, so they are more easily affected by interference from activations of neighbouring rows

Each time a row is activated, the word-line potential swings widely, making charge leak more easily from cells in nearby rows. As scaling shrinks the distance between cells, the interference becomes stronger, while the smaller cell capacitance also reduces the margin before a bit flips. Research has reported a tendency for newer DRAM generations to need fewer activations before the first bit flip. For this reason, countermeasures against Rowhammer become more important with each DRAM generation.

• A. Refresh is still needed after scaling; if anything, the margin for retaining data becomes smaller.
• B. Correct. Both the stronger interference and the smaller margin contribute.
• C. Repeatedly activating the same row is permitted as normal operation.