Apart from legal demand, why should a motorcyclist avoid driving in the center of the lane?

1. A Because it annoys car drivers
2. B Because the center of the lane is the dirtiest and most greasy part of a road.
3. C He is not prohibited from driving in the center of a two-way roadway, or in the center of a marked lane within a two way roadway.
4. D Because he should keep to the left and take account of other riders.