Bob has got good exam results. His parents are proud of his ______.
《云海》一文选自____,原题是____,作者是当代女作家____。
解不等式组: {2x+5>3(x−1)4x>x+72
菠菜浸泡在清水中,清水不变色;用开水浸泡菠菜后,水会变成绿色。这是因为菠菜细胞的什么结构被破坏()