In this factory trees are cut into pieces and then made ____ pap

In this factory trees are cut into pieces and then made ____ paper.
A、from
B、of
C、up of
D、into
【正确答案】：D
【题目解析】：made of 由……制成（看得出原材料）；made from 由……制成（看不出原材料），made into 被制成…… made up of 由……组成，句意：在造纸厂里，树被砍成小块，再制成纸。