The answer is D: test possible choices and then avoid ones that are not desirable.
The gasoline engine where the air and fuel mixture is burned is called the combustion chamber. A piston is used to increase and decrease the volume which prepares the fuel to be mixed with air. A spark plug is ignited then to create the combustion thereafter.
I think the Belt of the inter-tropical convergence zone is the general part of the general circulation found on the doldrums. This is a belt of low pressure which circles the Earth generally near the equator where the trade winds of the Northern and southern Hemispheres converge. Mainly characterized by convective activity which generates often vigorous thunderstorms over large areas.