[单选题]
A horizontal curve oe3 v/h)8d 1mrzr hqai.n 99aikj ok5r. 8nd0xtba bobsled run is banked at a $45^{\circ}$ angle. When a bobsled rounds this curve at the curve's safe speed (no friction needed to stay on the run), what is its centripetal acceleration?
A. $1.0 \; g$
B. $2.0 \; g$
C. $0.5 \; g$
D. none of the above
