Final answer:
Reset the alarm, remove the balloons, document the incident, possibly fill out an incident report, and leave a note for the client to inform them of what happened.
Step-by-step explanation:
Upon receiving a motion sensor alarm triggered by helium balloons, the correct course of action would be to reset the alarm, remove the balloons that caused the false alarm, document the incident in a memo book, and if required by the company's protocol, fill out an incident report when returning to the desk. Leaving a note for the client could also be a professional courtesy to inform them of the incident and the actions taken. It is important to address false alarms as ignoring them can lead to complacency and potentially missing genuine security threats in the future.