The Banking Angle in a Turn on the Olympic Bobsled

The banking angle in a turn on the Olympic bobsled track is not constant, but increases upward from the horizontal. Coming around a turn, the bobsled team will intentionally "climb the wall," then go lower coming out of the turn. Why do they do this?

A) to give the team better control, because they are able to see ahead of the turn
B) to prevent the bobsled from turning over
C) to take the turn at a faster speed
D) to take the turn at a slower speed
E) to reduce the g-force on them