One day some boys were playing by a pond. All (a) -—–— a sudden, they saw some frogs were swimming in it. They started throwing stones (b)——— them. Two or three frogs died (c) ———–it. One senior frog holding its head (d)———– said, “Please stop this cruel act of yours.” The boys said, “We are playing a game. We will not stop.” “What is a game for you is a cause of death (e)——-