Tailgating is the process of following a vehicle too closely without giving space. Tailgating is dangerous because when a vehicle follows another vehicle too closely it leaves no space to stop. It can be more dangerous when following heavy vehicles especially vehicles that are heavily loaded.
If someone tailgate's you then you should give warning before stopping. Tailgaters can be avoided by slowing down and allowing the tailgater to pass by. Or by changing the lane also.
In the given scenario, the tailgater should be allowed to pass by, by slowing down the vehicle.
So, the correct option is B.