Step 1: In a medicolegal autopsy the order in which body cavities are opened is not rigidly fixed. It is guided by the nature of the case and the suspected cause of death.
Step 2: The examiner finds it convenient to start with the cavity that is chiefly affected, so that the relevant findings are documented first and without disturbance.
Step 3: This means depending on the case, the thoracic, abdominal or cervical cavity may each be opened first. Therefore no single cavity is always the starting point, and any of the above can be correct.
Step 4: As a routine point, the spinal cord is not opened unless specifically indicated. Hence the best answer is any of the above.