The correct answer is option 2: "Conductivity of copper is more than that of stainless steel."

Stainless steel is a poor conductor of heat compared to copper. When cooking, it is important to evenly distribute heat throughout the pan to ensure food is cooked evenly. To address this issue, stainless steel cooking pans are fabricated with a copper bottom.

Copper is known for its excellent thermal conductivity, meaning it can transfer heat quickly and efficiently. By incorporating a copper bottom, the heat is conducted more evenly and efficiently across the pan`s surface. The copper bottom allows for rapid and uniform heat distribution, ensuring that food is cooked consistently.

It is important to note that the other options provided in the question are not entirely accurate. Option 1, stating that copper is cheaper, is not a valid reason for why stainless steel cooking pans have a copper bottom. Option 3, suggesting that copper increases the durability of the pan, is also incorrect. Option 4, stating that copper is a good reflector of heat, is not the primary reason why copper is used in the bottom of stainless steel cooking pans.