The correct answer is - False.
When approaching a horseback rider on a country road, you should never blow the horn as a sign of your presence. The reason for that is that the horn will scare the horses, and once panicked they may injure the rider or themselves.
The best way is to slow down from some distance away while approaching. Than pass by them with the least noise possible, and also by leaving about one car space in between, and once they are passed slowly increase the speed.
