How should you turn left from a road on which the following sign is placed?

1. You should start turning from the central lane.
2. Correct answer: From the left side, unless otherwise signposted.
3. You should turn from the far right lane.
4. It is forbidden to turn left. You are only allowed to drive forward.

WhyA blue square with an arrow up means a one-way road. On it you turn left from the left side of the roadway, unless signs say otherwise.