A

Reasoning: Rapid fluid resuscitation is achieved with the largest-bore peripheral catheter (14–16 G). A grey cannula is 16 G, allowing a markedly higher flow rate than green (18 G), pink (20 G) or blue (22 G) catheters; experimental work shows flow through 14–16 G cannulae is more than double that of 18 G and far exceeds smaller gauges, making them the standard recommendation for emergent volume replacement [Khoyratty, 2016, 27185686; Hoelzer, 1986, 3522202].