They ____ ____ the idea of helping the old at weekends.

下列物质中，属于合成纤维的是（　　）

阅读《春兴》一诗，完成下面题目。
                                                                                                                春  兴

                                                                                                         （唐）武元衡
                                                                                        杨柳阴阴细雨晴，残花落尽见流莺。 
                                                                                        春风一夜吹乡梦，又逐春风到洛城。