[单选题]
The maximum speed around a level curve i 9*q(3 sq)xzjn 6w7+awdaxdzl s 30.0 km/h. What ;.eiy)51l9h3zcgf fyr gg9 geis the maximum speed arounelg ;g59e rcgzf)g1.h9y3 f yid a curve with twice the radius? (Assume all other factors remain unchanged.)
A. 42.4 km/h
B. 45.0 km/h
C. 60.0 km/h
D. 120 km/h
