To allow cyclists to position in front of other traffic
These are known as advanced stop lines. When the lights are red (or about to become red) you should stop at the first white line. However if you have crossed that line as the lights change you must stop at the second line even if it means you are in the area reserved for cyclists.
B To allow taxis to position in front of other traffic
C To allow people with disabilities to cross the road
D To allow cyclists and pedestrians to cross the road together