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。