Which of the following is a characteristic of backdraft?

A characteristic of backdraft is that it often presents with smoke-stained windows. When a fire consumes available oxygen in a confined space without airflow, it can create a buildup of smoke and heat. If the fire is then suddenly provided with more oxygen – for instance, when a door or window is opened – a backdraft can occur, resulting in a rapid ignition of the accumulated gases. The presence of smoke-stained windows indicates that smoke has been in contact with the glass for an extended period, which is typical in environments where backdrafts are a risk.

Other choices like visible flames throughout the space, open flames pushing out through seams, and brightly colored flames in high concentrations are usually indicative of different fire situations rather than specifically associated with backdrafts, which primarily involve smoky, oxygen-depleted environments.