What is an example of a suspicious item that may require closer inspection?

A backpack left unattended for an extended period is a clear example of a suspicious item that may warrant closer inspection. Such an item can raise significant safety concerns in public spaces like airports or train stations, where security threats can potentially arise from abandoned belongings. The nature of a backpack suggests that it could contain personal belongings, which might include items that could pose a risk. For instance, it could potentially be used to conceal dangerous materials or contraband.

In contrast, a ticket left unattended may not pose the same level of concern, as it is a document that does not typically contain anything hazardous. A travel brochure is simply informational and would not generally be associated with any security threats. Similarly, a cell phone charger, while it could be misplaced, does not evoke the same level of alarm as a backpack could, especially in a busy public environment where security needs to be vigilant.