下列有关生物学实验的叙述中,正确的是( )
A:用无水乙醇或丙酮提取、分离紫色洋葱鳞片叶中的色素
B:用紫色洋葱鳞片叶表皮细胞观察质壁分离时看不到染色体
C:观察线粒体用新鲜的藓类叶片代替口腔上皮细胞效果更佳
D:粗提取DNA实验中,用0.14mol/LNacl溶解DNA
The book was written in _______ easy English _______ even primary school students could understand it.
地球公转产生的自然现象是( )