If you delete the Width expression from the Expressions dialog box with Length=Width*2 defined, what will happen?

When you define a relationship between expressions in Siemens NX, such as Length being equal to Width multiplied by 2, the expressions become interdependent. In this case, if you attempt to delete the Width expression from the Expressions dialog box, the software will prevent you from doing so because it recognizes that Length is reliant on the value of Width. Since Length's value is derived from Width, removing Width would make it impossible to maintain the definition of Length.

The software's design is to preserve these relationships to avoid creating ambiguities in the model. Removing a crucial part of an expression that is fundamental to another will not be allowed, ensuring that critical dependencies between variables are maintained for the integrity of the design. Thus, the correct answer highlights the software’s protective mechanism that ensures consistency within the defined expressions.