make use of是什么词性的短语,of是介词,后为什么加to do

make use of是什么词性的短语,of是介词,后为什么加to do
We are making use of new machines to produce more products.
She made use of her hands to make money before

make use of ...是属于及物动词短语,后面的of是介词呀,已经接了介词of 的宾语new machines//her hands 嘛,再接to produce.//to make money...的不定式表示的是目的“为了做...//来做...”.
另一个列子：Do you know what use that peaple in the past __________ stones --- Yes,to make fire
A.were made of B.were made C.make of D.made of
答案是 D