The core of a cross section, also known as the kernel, is the region within which if a load is applied, the section will experience only compressive stresses and no tensile stresses. 
Option 3 is incorrect because if the load is within the core, there will be no tensile stresses. Tensile stresses occur when the load acts outside the core. This concept is crucial in structural engineering to ensure that materials such as concrete, which are weak in tension, do not experience tensile stresses.