Across common crude fractions, identify which cut generally contains the maximum sulphur under typical refinery slates: diesel, gasoline, naphtha, or atmospheric residue.

Introduction / Context:
Sulphur is naturally present in crude oil as organosulphur compounds. Its distribution varies by boiling range; heavier fractions typically carry higher sulphur and more complex species, challenging desulphurization.

Given Data / Assumptions:

• Fractions compared: gasoline, naphtha, diesel, atmospheric residue.
• Modern refineries often hydrotreat light streams to very low sulphur.
• Crude slate and processing affect absolute values but not the general trend.

Concept / Approach:
Heavier fractions (residua) hold larger, more refractory sulphur compounds (e.g., polyaromatics with sulphur). Light fractions can be upgraded to ultra-low sulphur via hydrotreating, while residue remains sulphur-rich unless subjected to deep conversion (coking, resid hydrodesulphurization).

Step-by-Step Solution:

Verification / Alternative check:
Assay data consistently show higher sulphur content in residua compared with lighter cuts.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming retail diesel sulphur levels reflect untreated streams; finished diesel is hydrotreated to spec.

Final Answer:
Atmospheric residue