题目

Once upon a time the frogs decided to ask Jupiter, the king in Roman mythology(罗马神话), for a king of their own. Jupiter felt it funny. “Here you are,” he said, throwing a log(原木) of wood with a splash into the lake where they lived. “Here is a king for you.”The frogs dived under the water in fright, going as deep into the mud as they could. After a time one of the braver ones swam carefully to the surface to take a look at the new king.“He looks very quiet, “said the frog. “Perhaps he is asleep.” The log stayed quite still on the smooth lake and one by one more frogs请写出一个是中心对称图形的几何图形的名称： ．