You are driving on a road with marked lanes and you are in the lane with an arrow showing a left turn only. What must you do?

The correct answer is: Left turn

According to New Zealand road traffic rules, when a driver is in a lane marked with an arrow indicating left turn only, they must follow the arrow's direction and turn left. This means that if you are in such a lane, you are only permitted to turn left; going straight or turning right is not allowed. The purpose of this regulation is to ensure the orderly flow of traffic and the safety of all drivers by reducing uncertainty in vehicle movement, thereby minimizing traffic congestion and potential accidents.