You develop a subVI that only outputs a value and need to use this subVI in a (calling) VI. Which of the following is the best way to enforce dataflow to control the execution of the subVI.

1. Use the subVI in a Sequence structure.
2. Modify the subVI to have dummy inputs that can be sued from the calling VI.
3. Modify the subVI to have Error clusters that can be used from the calling VI.
4. Modify the subVI to have a global variable and use it from the calling VI.