Final answer:
The upper and lower yield points are observed in carbon steels. Therefore, the correct option is B
Step-by-step explanation:
The upper and lower yield points are observed in carbon steels.
Carbon steels are alloys of iron and carbon, where carbon is the primary alloying element. These metals undergo a unique phenomenon known as yield point phenomena.
Below the upper yield point, carbon steels exhibit elastic deformation, meaning they can be bent and return to their original shape. However, beyond the upper yield point, they start showing plastic deformation or permanent change in shape.