A vehicle placarded for Division 1.1, 1.2, or 1.3 explosives...

Answer: B — May be left unattended in a safe haven

A vehicle placarded for Division 1.1, 1.2, or 1.3 explosives can indeed be left unattended in a designated safe haven under specific conditions. Safe havens are predetermined locations where hazardous materials can be left temporarily without posing an immediate risk to public safety. The understanding is that these safe havens meet certain criteria that mitigate risks associated with the storage or handling of explosives. Though vehicles transporting explosives must generally adhere to strict regulations, which include monitoring and special handling requirements, the nature of safe havens allows for controlled situations where unattended storage is permissible. Regulations are in place to ensure that explosives are stored safely to reduce the risk of accidents or theft while they are left unattended for necessary durations. In contrast, continuous monitoring, special handling requirements, and weight limitations are typically associated with transporting explosives, but they do not negate the possibility of leaving the vehicle in an appropriate safe haven. Each of those other aspects plays a role in ensuring overall safety while maintaining certain operational allowances for secure settings.