A tortoise challenges a hare to a race.The hare eagerly agrees and quickly runs ahead,leaving the slow-moving tortoise behind.Confident that he will win,the hare stops to take a nap.Meanwhile,the tortoise walks at a slow steady pace for the entire race.The hare awakes and runs to the finish line,only to find the tortoise already there.Which of the following graphs matches the description of the race,showing the distance d traveled by the two animals over time t from start to finish？（　　）
一只乌龟向一只兔子挑战比赛。兔子欣然同意并迅速跑到前面，把动作缓慢的乌龟留在后面。兔子自信地认为他会赢，所以停下来小睡了一会儿。与此同时，乌龟以稳定的步伐走完了整个比赛。兔子醒来并跑到终点，只是发现乌龟已经到那里了。以下哪个图形描述了比赛的描述，显示了两只动物从开始到结束在时间t内走过的距离d？（　　）