Which step is not part of a normal convection cycle? A.
Unequal heating creates a pressure difference.
B. Air flows from a high-pressure area to a low-pressure area.
C. Cooled air sinks toward the surface, creating a low-pressure area
D. Warmed air sinks, creating a high-pressure area as it falls.
above it.

D.  Warmed air sinks  is not a normal convection cycle outcome

Explanation:

Warm air is buoyant and rises.  Cold air is dense and sinks.

Think of fog in the air.  Fog forms in low/cool areas, as the sun comes out and warms up the atmosphere the upper atmosphere, heat flows to cold so upper atmosphere air displaces the fog.

Space heating, the steam or hot water radiators are placed along the floor typically causing convection of warm air to rise up over windows and cold walls, breaking up cold air drafts.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds

thats not even an aswer choice