What is especially important when choosing the speed for driving along tree-lined avenues with narrow roadways?

The selected combination of answers is correct because it emphasizes both the need to estimate lateral distances to trees and oncoming traffic and the necessity to potentially stop within half the visible distance when encountering a wide vehicle.

In German traffic laws, particularly under the regulations governing safe driving in narrow areas, it's important to maintain a safe distance from obstacles like trees while also being aware of incoming traffic. This ensures that drivers can react appropriately and safely.

The first point reflects the importance of spatial awareness in tight driving situations, and the second point highlights the need for caution when larger vehicles are present, as they can require more space, which could affect your stopping distance. Both of these aspects contribute to safer driving practices, especially on tree-lined avenues with limited roadway space.