Convection
Convection is the transfer of energy by the bulk movement of a fluid that carries its internal energy along with it. AP Physics 2 names it as one of three thermal processes and treats it qualitatively.
Essential knowledge 9.3.A.2 lists convection as one of the three thermal processes by which energy may be transferred between systems at different temperatures, with conduction and radiation.
What separates it from conduction is that the matter moves. Conduction passes energy along a material that stays put; convection warms a mass of fluid, which typically becomes less dense, rises, and physically carries its internal energy somewhere else. No fluid, no convection. It cannot happen inside a solid and it cannot cross a vacuum.
AP Physics 2 gives convection no equation. The Thermal Physics group on the sheet holds eight entries, and the only transfer-rate equation among them is the conduction one, , which the CED files under 9.5.B.1. Topic 9.3 itself prints no equation and no boundary statement. So the exam asks you to identify convection as a pathway and to say what interrupts it, never to compute a convective rate.
Identifying pathways is the usable skill. Any object in contact with a fluid has a convection pathway to that fluid. A vacuum flask attacks all three processes at once: a gap to interrupt conduction, an evacuated gap so there is no fluid left to convect, and a silvered surface to cut radiation.