题目

Before they started out, they searched for some information on the Internet.(before doing) , they searched for some information on the Internet. 答案：【1】Before【2】starting out把红苋菜浸在冷水中，冷水不会变红，放入沸水煮几分钟，沸水变红．出现这种现象的原因主要是破坏了细胞中的（ ）A．细胞壁B．细胞膜C．细胞质D．细胞核