Final answer:
While the correct answer is not specified in the provided information, it is generally recommended to signal at least 100 meters before turning when driving at high speeds to ensure road safety, though local traffic laws should be consulted for specific requirements.
Step-by-step explanation:
When driving on a multi-lane highway at 100 km/h and wishing to turn onto another road, the appropriate distance to signal your intentions before making the turn is not specified in the information provided. However, many regions and driving manuals suggest signaling at least 100 meters before turning to ensure other road users are aware of your intention and to maintain safety on the road. This allows drivers in other vehicles sufficient time to react to your actions, especially when traveling at high speeds. Each country or region may have its own specific regulations, so it's essential to consult the local traffic laws for precise rules.