Basic composition of crude: Which statement about petroleum (crude oil) is correct considering its broad natural composition?

Introduction:
Petroleum is a complex natural mixture of thousands of hydrocarbons and non-hydrocarbon species. The question probes general truths vs common misconceptions about crude composition.

Given Data / Assumptions:

• We consider whole crude oils from conventional sources.
• Statements span optical activity, predominant families, and presence of asphaltics/aromatics.

Concept / Approach:
Natural crudes are predominantly mixtures of paraffins, naphthenes (cycloalkanes), and aromatics, plus resins and asphaltenes to varying degrees. Olefins are usually scarce in unprocessed crude due to geologic stability. Many crude components can exhibit optical activity (chiral species), and bulk crude samples often show measurable optical rotation.

Step-by-Step Solution:

Verification / Alternative check:
Crude assays and compositional overviews consistently show families PNA (paraffins-naphthenes-aromatics) with resins/asphaltenes; olefins are generated chiefly during cracking/upgrading, not present in bulk initially.

Why Other Options Are Wrong:

• (b): Misstates the main families.
• (c)/(d): Overly absolute; most crudes include asphaltics and aromatics.
• (e): Ignores the diversity of molecular structures present.

Common Pitfalls:
Confusing refinery products or reaction intermediates (olefins) with native crude composition.

Final Answer:
It is optically active.