[单选题]
The maximum speed ardi *w5b 9d1rqet7ftl2tx*s pw a-,z3nou7m bq(mgbn1/cw5g-hy ns7sr1nd a level curve is 30.0 km/h. What is the maximum speed around a curve with twice the radius? (Assume all other factors wqgnmc b/nrm(1s g175b-y 7hsremain unchanged.)
A. 42.4 km/h
B. 45.0 km/h
C. 60.0 km/h
D. 120 km/h
