The correct answer is D. High strength bolt.
High strength bolts are designed to withstand high tensile loads and are often used in applications where there is a risk of fatigue failure. They are made from high-strength steel and have a higher yield strength than other types of bolts. This means that they can be tightened to a higher level without the risk of deformation or failure.
Black bolts are made from low-carbon steel and are not heat-treated. They are not as strong as high strength bolts and are not suitable for use in applications where there is a risk of fatigue failure.
Ordinary unfinished bolts are similar to black bolts, but they are not coated with any type of finish. This means that they are more susceptible to corrosion and should only be used in applications where they will not be exposed to moisture or other environmental hazards.
Turned and fitted bolts are made from high-quality steel and are machined to precise tolerances. They are often used in applications where there is a need for a high degree of accuracy or where the bolt will be subjected to a lot of vibration.
In conclusion, the most suitable type of bolt for use in applications where the bolts are subjected to reversal of stresses is a high strength bolt.