In petroleum refining practice, sulphuric acid treatment (acid treating) of petroleum products is used to remove reactive impurities and improve stability. Identify which kinds of contaminant materials are predominantly removed by such acid treatment from refined streams (e.g., cracked naphtha, kerosene), considering gum-forming species, color-forming precursors, and asphaltic bodies.

Introduction / Context:
Sulphuric acid treatment (often called acid treating or acid wash) is a classical finishing step historically used on certain petroleum fractions such as cracked naphthas and kerosenes. The strong acidity and sulfonating ability of sulphuric acid selectively react with unsaturated, oxygenated, nitrogenous, and polyaromatic precursors that are responsible for color, gum formation, odor, and instability. Understanding exactly what gets removed clarifies why product appearance and storage stability improve after treatment.

Given Data / Assumptions:

• Stream: light to middle petroleum fractions (e.g., cracked gasoline, straight-run kerosene).
• Treating agent: concentrated sulphuric acid.
• Goal: remove instability and color bodies to improve product quality.

Concept / Approach:
Sulphuric acid reacts with and/or protonates reactive polar compounds, polymerizable olefinic species, diolefins, resin formers, and certain polycyclic aromatics. These transform into acid-soluble oils (ASO) and sludge that can be separated from the hydrocarbon phase. Because gum-forming and color-forming precursors overlap chemically with asphaltic/resinous bodies, a broad improvement is seen across several quality indicators.

Step-by-Step Solution:

Verification / Alternative check:
Refinery finishing literature documents the formation of acid sludge (ASO) containing polymerized unsaturates and colored bodies; post-treatment products show improved color and oxidation stability metrics (e.g., lower existent gum values).

Why Other Options Are Wrong:

Common Pitfalls:
Assuming acid treating is a deep desulfurization step; it is not a substitute for hydrotreating and is used selectively due to sludge disposal concerns.

Final Answer:
All (a), (b) & (c)