this pair of trainers is made_ leather(填介词）

OF
都是由什么组成
be made of 是可以看出原材料的,例:The sweater was made of woollen.
毛衣是羊毛作的(可以看出的)
be made from是不可以看出原材料的,例/:The paper is made from wood
纸是树木作的(看不出来的)