Answer: Technical B is right.
Step-by-step explanation:
The first systems injected air very close to the engine, either in the cylinder head's exhaust ports or in the exhaust manifold
However, the extra heat of recombustion, particularly with an excessively rich exhaust caused by misfiring or a maladjusted carburetor, tended to damage exhaust valves and could even be seen to cause the exhaust manifold to incandesce.