In New Zealand, drivers should avoid any behavior that may distract them, as such actions can pose a threat to driving safety. The correct option is "3. Observing vehicle mirrors," as this is an important and necessary safety measure while driving, helping to ensure that the driver has adequate awareness of their surroundings and can avoid potential dangers.
1. The options "Eating and drinking" and "Using a mobile phone" both clearly distract the driver's attention and increase the risk of accidents. In New Zealand, it is explicitly illegal to use a mobile phone while driving, and it is only permitted to use a phone in a safe and lawful manner (such as using hands-free devices).
2. "Being ill," while not a choice made by the driver, should also be avoided if it affects driving ability. If the illness impacts the driver’s reaction time and judgment, it may lead to unsafe driving conditions.