ANS:B - improve ductility.

Normalizing of an object typically does not improve ductility, yield strength, or mechanical properties significantly. Instead, its primary purpose is to refine the grain structure of the material, particularly if it has been subjected to hot working processes. Here's an explanation of each point:

1. Refining coarse grain structure obtained during hot working: This is true. Normalizing involves heating the material to a specific temperature above its critical range and then allowing it to cool in still air. This process helps to refine the grain structure, making it more uniform and smaller. It eliminates any coarse grains that may have formed during hot working processes like forging or casting.
2. Improving ductility: Normalizing typically does not have a significant effect on ductility. While it may result in some improvement due to the refined grain structure, the primary purpose of normalizing is not to enhance ductility.
3. Improving yield strength: Normalizing may slightly affect the yield strength, but its primary effect is on refining the grain structure rather than directly influencing yield strength.
4. Improving mechanical properties: While normalizing can contribute to overall improvements in mechanical properties by refining the grain structure, its effects may not be as pronounced as those achieved through other heat treatment processes like quenching and tempering.