Final answer:
Safety hooks or shackles in engineering must meet certain tensile strength standards for safety. The standard value for such components is usually not less than 20 kN, but it can vary based on specific industry regulations.
Thus, the correct oprtion is B.
Step-by-step explanation:
The question is about the minimum ultimate tensile strength required for safety hooks or shackles made of drawn, rolled, or forged steel used in engineering applications, particularly within a safety context. According to most industry standards, safety equipment like hooks and shackles must have an ultimate tensile strength that provides an adequate safety margin beyond the actual forces they are expected to encounter during normal use. Considering the typical values provided in safety standards, the ultimate tensile strength for such safety components should not be less than 20 kN. However, the value may vary depending on specific regulations or standards applicable to the industry or region.
Therefore, the correct oprtion is B) 20 kN