Final answer:
The main concern when following a car in the acceleration lane is to maintain a safe following distance, allowing for sufficient reaction time and safe merging.
Step-by-step explanation:
When following a car in the acceleration lane, your main concern should be D) Maintaining a safe following distance. This ensures you have enough time to react and adapt to the traffic conditions as you prepare to merge onto the freeway. Staying too close to the car in front of you could lead to an unsafe situation if they brake suddenly, while accelerating to pass them or merging too quickly could disrupt the flow of traffic and increase the risk of a collision.