Correct option is D
BSW (British Standard Whitworth) is one of the earliest standardized thread systems developed by Sir Joseph Whitworth. It is characterized by a 55° thread angle and rounded crests and roots, which help reduce stress concentration and improve fatigue resistance. BSW threads were widely used in British engineering industries before the adoption of ISO metric threads.
The other options are incorrect because they are either wrongly expanded forms or non-existent terms. For example, “British Standard Weight” and “Bharath Standard Whitworth” are not recognized thread standards.
