The correct option is B 6 km/s
Let's convert all the given unit in m/s.
~ 2 m/s
~ 6 km/min =6×1000 m60 s=100 m/s
~ 6 km/s = 6×1000 m1 s=6000 m/s
~ 2000 m/s
Therefore when we arrange in descending order,
6000 m/s > 2000 m/s > 100 m/s> 2 m/s
So the fastest speed among the given is 6000 m/s or 6 km/s.