Final answer:
If a patient has been placed on a telemetry monitor, the task should be performed and charted in the patient's chart.
Step-by-step explanation:
If a patient has been placed on a telemetry monitor, the task should be performed and charted in the patient's chart. This means that option D, 'Open patient chart', is the correct choice. The telemetry monitor provides continuous monitoring of the patient's heart rate, rhythm, and other electrocardiogram (ECG) data. The information obtained from the monitor should be recorded in the patient's chart for documentation and future reference.