用一根玻璃针将一个变形虫（注：变形虫的身体就是﹣个细胞）切为两半，有核的一半能继续存活、无核的一半死亡．如果将一个变形虫的核取出、无核部分能短期生存，但不能繁殖后代，单独的细胞核则不能生活下去．如果在去核后三天、再植入一个细胞核，这个变形虫能生活正常．如图所示．

据图回答问题：

（1）____ 在细胞产生后代的过程中起主要作用．

（2）正常细胞的细胞核与细胞质的关系是____ ．

（3）从上述实例可知，细胞能正常完成多项生命活动必须具备的条件是____ ．

盲人用手指来“阅读”盲文，利用的是皮肤的（　　）

阅读短文，下列问题

    In the world today, all of the people need to have fun when they are free. We can't work all the time if we are going to keep healthy and enjoy life.

    Everyone has his own way of relaxing. Perhaps the most popular form (形式) is to take part in sports. There are team sports, such as basketball and football. There are also individual(个人的) sports, such as swimming and running. Skating and mountain climbing are the most popular recreation (消遣) for people who like to be outdoors.

Not everyone who enjoys sports likes to take part in them. Many people like watching them on TV or listening to them on the radio. So many people like some indoor relaxation, such as watching TV, singing and dancing.

    It doesn't matter if we like indoor recreation or take part in outdoor sports. It is important for everyone to relax from time to time, and enjoy some themselves.