Which of the following is illegal when parking your vehicle?

Parking in an unmarked crosswalk is illegal because it obstructs pedestrian pathways and poses a risk to both pedestrians and drivers. Crosswalks are designated areas meant for pedestrians to safely cross the street, and parking your vehicle in these areas limits visibility and accessibility, creating a hazard.

In contrast, parking in a designated parking space is permitted as these areas are specifically allocated for parking. Curbside parking can also be legal if you're following local regulations. Parking lots are constructed for the purpose of vehicle parking, and as long as you're within the boundaries and following any posted rules, it's allowed. Thus, parking in an unmarked crosswalk clearly violates traffic laws aimed at ensuring public safety.