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
