A:用猪血为实验材料的原因是猪血的红细胞有细胞核,DNA含量多
B:利用 DNA 在2mol/L的氯化钠溶液中溶解度最低,易析出的特性提取DNA
C:利用 DNA 不溶于酒精,而细胞中的其他物质可溶于酒精的特性提纯DNA
D:利用DNA与二苯胺作用而显现紫色的特性鉴定DNA
给加下划线的字注音,根据拼音写汉字。
(1)搏击____ (2)丰硕____ (3)无与(lún)____ 比 (4)顶(lǐ)____ 膜拜
阅读下面短文,掌握其大意,并根据所给字母的提示,写出一个英语单词的完整、正确形式,使短文通顺。
More and more A____ are going to work by bike. Do you know why more people are riding bikes to work? We can answer the question in d____ ways. First, bikes don't need gasoline(汽油),so it takes little m____ to use them. S____ a bike doesn't need much space, so it is e____ to find a place for it. And to ride a bike is good for one's h____ .People often d____ their cars to offices or to shops in the past. But now people think riding bikes is a good way of d____ sports. That's w____ more Americans are now riding to work by bike, and they are leaving(把...留下)their o____ cars at home.
世界上流经国家最多的河流和世界上最长的河流是( )
下列各句中,没有语病且句意明确的一句是( )