Concept:Stamina means the physical or mental strength to keep going for a long time.Explanation:In this sentence, Marian cannot run the race because she lacks staying power.The word closest in meaning to “stamina” here is “energy”.“Courage” is bravery, not physical endurance.“Determination” is a mental resolve, not physical capacity.“Ability” is too general; it does not carry the idea of sustained effort.Answer:B. energy