题目

C You’ve heard that plastic is polluting the oceans—between 4.8 and 12.7 million tonnes enter ocean ecosystems every year. But does one plastic straw or cup really make a difference? Artist Benjamin Von Wong wants you to know that it does. He builds massive sculptures out of plastic garbage, foreing viewers to re-examine their relationship to single-use plastic products. At the beginning of the year, the artist built a piece called “ Strawpocalypse, ” a pair of 10-foot-tall plastic waves, frozen mid-crash. Made of 168,000 plastic straws collected from several volunteer beach cleanups, 下列图形中：①线段；②正方形；③圆；④等腰梯形；⑤平行四边形．是轴对称图形的有______个．