Mechanical properties — typical minima for steel materials: Select the correct set of statements regarding common steel grades used in structural practice.

Introduction / Context:
Structural design relies on characteristic mechanical properties such as tensile strength, yield stress, and ductility (elongation). Familiarity with typical minima for different steel products helps in selecting materials and checking compliance with specifications.

Given Data / Assumptions:

• Traditional units kg/mm^2 used (1 kg/mm^2 ≈ 9.81 MPa).
• Properties quoted are typical minima for specification compliance.
• Elongation is referred to a proportional gauge length 5.65√A.

Concept / Approach:
Cast steels generally have lower yield stress relative to tensile strength; mild steels exhibit balanced strength and ductility; high tensile steels provide higher strength levels. The statements list representative baseline values consistent with many older specifications and handbooks.

Step-by-Step Solution:
Step 1: Check steel castings: 41 kg/mm^2 ultimate and 20.5 kg/mm^2 yield are standard minima.Step 2: Check mild steel: about 44 kg/mm^2 ultimate with ≈ 23% elongation at 5.65√A is typical.Step 3: Check high tensile steel: ultimate around 58 kg/mm^2 is a common minimum threshold.Step 4: All three statements are consistent; hence “All of the above”.

Verification / Alternative check:
Converting to SI: 41 kg/mm^2 ≈ 402 MPa, 44 kg/mm^2 ≈ 431 MPa, 58 kg/mm^2 ≈ 569 MPa, aligning with expected ranges for these products.

Why Other Options Are Wrong:
Any single-statement option omits other true statements; “None” is incorrect because all are valid.

Common Pitfalls:

• Confusing yield stress with ultimate tensile strength.
• Ignoring ductility criteria like elongation at specified gauge length.

Final Answer:
All of the above