Aluminum isn’t found free in nature, owing to its always with other elements, most common

Aluminum isn’t found free in nature, owing to its always with other elements, most commonly with oxygen.
A. being combined
B. having combined
C. combine
D. combined

(答案→)A. being combined B. having combined C. combine D. combined解析：combine …with…与……结合；这里owing to中的to是介词，故它的后面应跟动名词，这里是its+动名词也就是动名词的复合结构。又因为its与combine之间是被动关系，故用being combined。句意：在自然界中发现的铝不是自己存在的，因为铝和其它元素结合在一起，通常情况下是和氧在一起。故选A。

和我的回答一样，看来我也对了