It is illegal to follow a fire vehicle or ambulance responding to a call within...?

Answer: B — 150 metres

Following a fire vehicle or ambulance while they are responding to a call can be dangerous as they may need to make sudden stops or turns. This is why it is illegal to follow them within a set distance. Option A and C are incorrect because they are both too close to safely follow a responding vehicle. Option D is also incorrect as it is too far away and may lead to drivers not being aware that an emergency vehicle is approaching. Therefore, option B, 150 metres, is the most appropriate and safe distance to follow a fire vehicle or ambulance responding to a call.