硫铵萃取的目的是回收来自中和分离器硫铵母液中大约1%的己内酰胺。
参考答案:对
His parents wouldn’t let him marry anyone ______family was poor.
A.that
B.which
C.whom
D.whose
开始工作前,必须按规定穿戴好()。
A、衣物、手套
B、衣物
C、衣物、眼镜
D、防护用品