of which的用法及例句

　　The cell is the unit of which all living organisms are composed.

　　细胞是构成一切生物的`单位。

　　The trip was magical; the stuff of which dreams are made.

　　那是一次奇妙的旅行，宛如梦境。

　　I saw three camp beds, two of which were occupied.

　　我看见了3张折叠床，其中两张已有人占了。

　　Many theories on punishment exist, all of which are variations on a theme.

　　关于惩罚的理论有很多，虽形式略有不同，但其主旨都是一样的。

　　We are dealing with an epidemic the likes of which we have never seen in this century.

　　我们面临的疫情规模在本世纪尚属空前。