日日人人_亚洲美女在线视频_av手机在线播放_国产大片aaa_欧美中文日韩_午夜理伦三级

A.107             B.108              C.108           D.109

A.108                                                              B.107

C.106                                                              D.109

A.107           B.108            C.108             D.109

已知為等差數列的前n項和，且，有下列四個命題：

(1)；(2)；(3)；(4)數列中的最大項為．其中正確命題的序號是________．