问题
单项选择题
The tremendous heat at a star’s core,（）tremendous gravity, joins the nuclei of hydrogen atoms.
A. combined with
B. having combined with
C. combining with
D. being combined to
答案
参考答案：A
解析：
combined with此处表示一种一般情况，相当于when (it is) combined with，所以无需时态变化。
