Correct Option: A

obstacle (Noun) : hindrance; hurdle
hurdle (Noun) : obstacle
ban (Noun) : an official rule that says that something is not allowed
hedge (Noun) : a row of bushes or small trees planted close together, usually along the edge of a field, garden or road
relay (Noun) : a race between teams in which each member of the team runs or swims one section of the race