第一步：取未受感染的体重相同的小鼠三只，标为1，2，3号，都摘除胸腺并用大剂量X射线照射；
第二步：分别接种等量的霍乱弧菌疫苗，测定并确定没有了免疫力（无抗体产生）；
第三步：分别向1，2，3号小鼠体内注射等量的新鲜T淋巴细胞液、新鲜B淋巴细胞液和？；
第四步：分别向三只小鼠接种等量的霍乱弧菌疫苗；在相同条件下饲养20天后，分别测定三只小鼠体内血清抗体的含量．
在朽木上往往会长出一些木耳，木耳在生态系统中属于（ ）
不等式(x2-1)(x2-6x+8)≥0的解集是
辛亥革命后，孙中山三民主义进行反对北洋军阀的斗争，其核心目标是( )
阅读理解，根据短文选择正确的一项
One day a policeman was walking in the park. He saw a man there. The man was holding a penguin（领着一个企鹅）. The man said to the policeman, “ I found this penguin this morning. What shall I do with it?”“Take it to the zoo,” said the policeman. The next day the policeman saw the man again. He was still holding the penguin. The policeman said, “Why didn't you take the penguin to the zoo?”“I did,” said the man. “I took him to the zoo yesterday. Today I'm taking him to the cinema.
