如果是定语从句，most of后面不接that而是接which，因为of是一个介词。例句：

1.There are a great number of books in the reading-room,most of which are about science books.

阅览室里有大量的书，其中大部分是关于科技方面的书。

2.Many fruits are in the basket, most of which are apples.

篮子里有很多水果，其中大部分是苹果。

3.There are many green plants in the park, most of which are flowers.

公园里有很多绿色植物，其中大部分是花。