What brevity code should be transmitted at line 9 when a vehicle-borne IED detonates and strange liquids are observed on casualties?

When a vehicle-borne improvised explosive device (IED) detonates and strange liquids are observed on casualties, the appropriate brevity code to transmit is C, which represents 'chemical.' This is because the presence of strange liquids in the context of an explosion raises the potential concern for a chemical agent, especially in scenarios involving hazardous materials.

Chemical agents are specifically designed to harm or incapacitate individuals, and the symptoms or signs observed in casualties, such as unusual liquids, could indicate exposure to such agents. Thus, reporting with the 'chemical' code is crucial for ensuring that the appropriate emergency response teams, such as hazardous materials or chemical response units, are dispatched to manage the situation effectively.

While other codes like 'biological' could pertain to various health concerns, they would typically be associated with living organisms or toxins rather than immediate physical threats from an explosion site. The 'explosive' and 'atomic' codes refer to other specific threats that would not align with the described incident of an IED detonation followed by unusual liquid exposure.