What will happen if you try to access a property of an undefined object?

When trying to access a property of an undefined object, an error occurs because JavaScript requires an actual object in order to retrieve properties. If the object you are trying to access is undefined, the JavaScript engine cannot perform the operation and will throw a TypeError. This error indicates that the code is attempting to access a property of a non-existent object, which is a violation of how JavaScript objects and properties are expected to behave.

In contrast, the other outcomes described in the choices would not accurately reflect the behavior of JavaScript in this scenario. The program will not run correctly when trying to access properties of undefined, it won't return null or undefined directly as a result of the operation; instead, it raises an error that interrupts the normal flow of execution, highlighting the need to check whether an object is defined before accessing its properties.