微量元素是指含量在0．01%以下的元素，其中_________有智力元素之称；缺少________会导致贫血（均填元素符号）
I；Fe
The soldiers were fighting bravely_____their people__________the invaders. [ ]
A. with; for
B. for; against
C. back; with
D. out; with
有毒气体探测仪能探测有毒、有害氧含量。
