What action should be taken for a suspected explosive device?

In the context of handling a suspected explosive device, contacting the Pilot in Command (PIC) is crucial because the PIC is responsible for the safety and security of the aircraft and all aboard. By notifying the PIC, the flight crew can initiate the appropriate emergency procedures, including assessing the situation, coordinating with security personnel, and communicating with local authorities. This action ensures that the situation is managed by trained personnel who can evaluate the risks and take immediate, informed action to safeguard passengers and crew.

The other options would not be as effective in ensuring safety. Informing passengers immediately may cause panic and hinder the crew's ability to manage the situation effectively. While contacting local authorities is essential, it is typically done after the PIC is informed and has established a plan of action. Waiting for further instructions could lead to delays that may exacerbate the danger posed by a potential explosive device. Therefore, the most direct and effective step in this scenario is to involve the PIC right away.