To overtake on a road with one lane in each direction, it is crucial to do so safely and without endangering other drivers. Here we explain why the correct answer is that you can only overtake several vehicles at once if you can return to the right without causing danger:

- **Safety when overtaking**: When overtaking, you must ensure there is enough space to return to your lane without interfering with oncoming traffic. This is essential to avoid head-on collisions.

- **Overtaking conditions**: If you see an oncoming vehicle while overtaking, you must reduce speed and return to your original lane. This ensures that no danger is caused to other drivers.

- **Completion of overtaking**: Once you have overtaken, it is important to return to your lane as soon as possible without forcing other drivers to change their speed. This is done by turning on the indicator lights to signal your intention to return to the right lane.

In summary, overtaking several vehicles on a single-lane road in each direction is allowed only if you can do so safely, returning to your lane without endangering oncoming vehicles.