What does the driver of vehicle 1 need to ensure prior to moving?

The correct answer focuses on the importance of ensuring that the driver has the right-of-way before moving. In driving scenarios, understanding right-of-way rules is crucial for maintaining safety and preventing accidents. Having the right-of-way means that the driver has the legal privilege to proceed without yielding to other vehicles or pedestrians, under the specific conditions of the traffic situation.

Before proceeding, the driver must confirm that they are legally allowed to move without interfering with other road users who might have priority. This practice not only helps in preventing collisions but also plays a vital role in the overall traffic flow and order on the road. Ensuring that one has the right-of-way is fundamental to responsible driving, as it demonstrates awareness and adherence to traffic laws and regulations designed to protect everyone on the road.

The other options, while potentially relevant to specific scenarios, do not encompass the overarching principle of traffic laws regarding priority. For instance, checking if other vehicles are stopped or have completed their maneuvers is essential but not sufficient on its own without the broader awareness of right-of-way.