Which command would be used to create a pattern that varies in length?

The command that allows for the creation of a pattern that varies in length is known as the General command. This command is designed to create complex patterns where the instances can be modified in terms of their position, count, and especially their length. This flexibility enables users to specify unique dimensions for each instance in the pattern, accommodating designs that require non-uniform spacing or varied lengths.

In contrast, the other options are more suited for creating uniform patterns. Pattern Geometry generally refers to creating a regular pattern based on selected geometric entities, and it typically maintains a consistent length or spacing between instances. Pattern Feature is often used for repeating features in a consistent manner within the model, adhering to typical dimensions. Instance Array is similar, focusing on duplicating feature instances equally across defined parameters.

Overall, the General command provides the necessary adaptability for patterns that differ in length, making it the most suitable choice for this particular requirement.