Final answer:
When entering an expressway behind several other vehicles, the most important action is to adjust your speed to match the flow of traffic to ensure a safe merge. Neither stopping on the ramp nor moving alongside other vehicles is safe or correct.
Step-by-step explanation:
When entering an expressway behind several other vehicles, it is most important to adjust your speed to the flow of traffic and merge safely. This means you should accelerate to a similar speed as the traffic on the expressway to allow for a smooth and safe entrance. Trying to run alongside or toward any vehicle on the expressway is dangerous and not advised. Moreover, stopping and becoming stationary on the entrance ramp can cause accidents and is also not correct. Instead, focus on the traffic patterns and adjust your speed accordingly to merge safely without causing disruptions in the flow of traffic.