many ways have been found_small and simple machines to process
问题描述：
many ways have been found_small and simple machines to process
large and complicated machine parts
a by using
b to use
c using
d used
答
首先,排除c,d选项,表被动的been found不可以直接接动词 后应调整语序（to process指得到处理,来处理的意思,先省略）many ways to use small and simple machineshave been found many ways by using small and sim...