What should you do to help protect the environment?

The combination of choices you selected is correct because it covers key actions that contribute to environmental protection while driving.

1. Having the motor vehicle inspected if the exhaust emits excessive smoke is essential because it ensures the vehicle complies with emissions standards, thereby reducing air pollution. Regular inspections are mandated in Germany under the Environmental Protection Act.

2. Switching off the engine when waiting for longer periods is a good practice that helps to minimize unnecessary fuel consumption and reduce exhaust emissions. This aligns with the principles of eco-friendly driving encouraged by German traffic regulations.

3. Avoiding unnecessary driving back and forth reduces fuel usage and minimizes traffic congestion. This is in line with environmental initiatives promoted by German traffic laws, which aim to promote sustainable transportation practices.

By selecting all three actions, you demonstrate an understanding of the broader responsibility drivers have for environmental protection, which is a key aspect of modern driving regulations in Germany.