Older RTs scale as a near-linear stretch of younger RTs

Correct: B — A near-linear stretching of younger RTs by a multiplicative factor

Plotting older-adult mean RTs against younger-adult mean RTs across many tasks (a Brinley plot), Cerella (1985) reported a near-linear relationship with slopes of roughly 1.4–1.6: for any given task, older adults' RTs were a multiplicative stretch of younger adults', not a constant additive lag. The pattern argued for a domain-general slowing — every stage scales by the same factor — and provided the empirical engine that Salthouse later formalized as processing-speed theory. Modern reanalyses qualify the picture (slopes differ for verbal vs. spatial tasks; intercepts matter), but Brinley-plot scaling remains the standard summary of cognitive slowing.