Explanation:

- The idiom "call upon" generally means to formally request or invite someone to do something. It can be used in various contexts, such as asking for help or guidance.

- Option 1: "To adjust" means to change or modify something to fit better or work more efficiently. This doesn't match the meaning of "call upon."

- Option 2: "To stop" indicates bringing something to a halt or end. This is unrelated to the idiom in question.

- Option 3: "To order" implies giving a command to someone. This can sometimes align with "call upon," especially if a formal request is considered a kind of order.

- Option 4: "To follow" means to go after or pursue someone or something. This doesn't align with the idiom.

Option 3: To order - While this isn't the perfect match, it can sometimes be relevant.