【单选题】下列哪种制备方法是控制均匀沉淀的有效方法()
C.
在金属盐溶液中加Na 2 CO 3 作沉淀剂
【单选题】'He was on his way' refers to the fact that __.
A.
he gave up and returned home
B.
he began to work towards success
C.
he took a journey to Hollywood
D.
he had difficulties in playing the small part
【单选题】After his long journey, he his home yesterday. [ ]
【简答题】通过改变氧气和乙炔气体的体积比,可得到 焰、 焰和 焰 三种不同性质的气焊火焰。