一次性坩埚不需清洁、烘干，对净化钢质、降低夹杂率、提高焊头质量十分有利。
参考答案：对
Vicky, _____ born in China, lived and practiced law in public.
A．was
B．he was
C．although
D．who he was
矿物的突起等级可分为哪几种？如何确定未知矿物的突起等级？
