The correct answer is D. None of these.
The speed of a lorry during poor visibility should be determined by the road conditions and the driver’s judgment. There is no one-size-fits-all answer, as the safe speed may vary depending on the specific circumstances.
In general, it is advisable to drive more slowly in poor visibility. This will give you more time to react to hazards and avoid accidents. It is also important to be aware of the other drivers on the road, as they may be driving more slowly than usual.
If you are driving in very poor visibility, it may be best to pull over and wait until conditions improve. This is especially important if you are driving on a winding or unfamiliar road.
Ultimately, the safe speed of a lorry during poor visibility is up to the driver. It is important to use your judgment and drive at a speed that is safe for the conditions.