Engine Materials — What are common cylinder block materials? Select the most typical material combination used for engine cylinder blocks in automobiles.

Introduction / Context:
Cylinder blocks must provide strength, wear resistance, and good thermal behavior. Historically, cast iron dominated due to strength, machinability, and bore durability; many modern engines use aluminium alloy blocks for mass reduction and faster warm-up, often with liners or coatings.

Given Data / Assumptions:

• Mainstream passenger and light-commercial engines.
• Blocks may be grey cast iron or aluminium alloy (with liners or surface treatments).
• Focus on the block material, not heads or liners alone.

Concept / Approach:
Cast iron blocks offer rigidity and excellent wear; aluminium blocks reduce mass and improve vehicle dynamics and fuel economy. Both are widely used. Steel and brass are not typical block materials; steel is difficult for economical casting/machining in this application, while brass lacks high-temperature strength and is costly.

Step-by-Step Solution:
Identify mainstream choices: cast iron (grey or CGI) and aluminium alloy.Reject atypical combinations (steel, brass, magnesium for blocks).Thus the correct pair is cast iron and aluminium alloy.

Verification / Alternative check:
Survey of OEM engines shows extensive use of both materials; aluminium blocks often have cast-in iron liners or plasma-sprayed bores to ensure wear resistance.

Why Other Options Are Wrong:
Cast iron and steel: steel not typical for full blocks.Steel and aluminium alloy: again, steel blocks are rare and impractical.Brass and steel; magnesium and wrought iron: unsuitable for cost, strength, and thermal reasons.

Common Pitfalls:
Assuming aluminium always saves weight without trade-offs; it may need liners or special coatings.

Final Answer:
cast iron and aluminium alloy