Solution:

In petroleum refinery engineering, the smoke point of kerosene refers to the maximum height of flame (in mm) without causing smoking, when burnt in a standard lamp (Option C).

The smoke point is an important parameter that indicates the quality of kerosene or other liquid fuels. It represents the maximum temperature at which the fuel can be burned without producing visible smoke. When the flame exceeds this height, incomplete combustion occurs, resulting in the emission of smoke.

Therefore, the correct option is Option C: Maximum height of flame (in mm) without causing smoking, when burnt in a standard lamp.

Solution:

In petroleum, the constituents responsible for ash formation are typically organometallic compounds. These compounds contain both organic (carbon-based) and metal components. During the refining process, when petroleum is subjected to high temperatures and pressure, these organometallic compounds can decompose and leave behind solid residues, forming ash.

Therefore, in this context, the correct option is Option B: Organometallic compounds.