题目

_______ many scientists believe is ______the continuous presence of water benefits the earth a lot. A . What, which B . Which, that C . When, that D . What, that 答案：D高等植物叶肉细胞和肌肉细胞内都具有，而蓝藻细胞内不具有的结构是（ ）A.线粒体和中心体B.染色体和核糖体C.内质网和叶绿体D.高尔基体和线粒体