阅读短文，判断下列句子分别符合A、B、C哪一项。

    Hello! My name is Jack. I'm eleven. I'm a student. I study in the Fifteenth Primary School. I'm in Class 4, Grade 5. There are 45 students in my class. They are 22 girls and23 boys. We have English, Chinese, maths and other subjects.

    This morning I was the first one to get to school.John was the second one. Ann and Amy were the third and the fourth. We are in the same class. We have English lessons in the sixth classroom. Our classroom is on the fourth floor of our school building.

促成俄国十月革命条件成熟的客观因素是（   ）

若要制备杂交瘤细胞，需取免疫后小鼠的B淋巴细胞（染色体数目40条），并将该细胞与体外培养的小鼠骨髓瘤细胞（染色体数目60条）按一定比例加入试管中，再加入诱导剂诱导细胞融合，经筛选培养及抗体检测，得到不断分泌抗A抗体的杂交瘤细胞．

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