Answer : 2. "will decrease"
Explanation :

When a copper disc with a circular hole in the center is heated, the diameter of the hole will generally increase. This phenomenon occurs due to the expansion of the copper material as it is heated. When a material is heated, its particles gain energy and move more vigorously, leading to an increase in volume, and consequently, an increase in the diameter of the hole and the entire disc. The exact amount of expansion would depend on factors such as the temperature increase and the material properties of copper.