精子和卵细胞的结合场所是在（    ）

阅读下面短文, 按照句子结构的语法性和上下文连贯的要求, 在空格处填入一个适当的词或使用括号中词语的正确形式填空。

    Itzhak Perlman is ____ famous violinist. He was born ____ 1945. He once gave a concert in New York City. Getting on stage was difficult for him ____ he is disabled. The audience sat ____ (quiet) while he made his way across the stage to ____ (he) chair. Then he picked up the violin, ____ (put) it under his chin (下巴) and started to play. But this time, when he finished the ____ (one) part, one of the ____ (string) on his violin broke. ____, he continued to ____ (play) the music. The music he played with three strings sounded even more wonderful than it was played with four strings.

之所以说俄国1861年改革是一次资产阶级性质的改革，其主要依据是（ ）