In an **acceleration lane**, it is important to know where to stop to yield if necessary. The correct answer is to stop **at the beginning of the lane**. This is because, by stopping at the start, you avoid entering the main traffic flow without having enough space to maneuver or accelerate properly.

- **Visibility and safety**: By stopping at the beginning, you have better visibility of the traffic on the main road, allowing you to assess when it is safe to merge. This is similar to what is recommended at intersections, where you should wait in a place where you can clearly see the traffic before proceeding.

- **Avoiding obstructions**: Stopping at the beginning of the acceleration lane also helps avoid getting stuck in the middle of the lane, which could obstruct the passage of other vehicles also trying to merge.

In summary, stopping at the beginning of the acceleration lane is the safest and most efficient option for yielding, as it allows for better traffic assessment and avoids unnecessary obstructions.