每做一次焰色反应实验,都要用一种试剂洗净铂丝,这种试剂是
A.稀盐酸
B.NaOH溶液
C.稀硫酸
D.Na2CO3溶液
答案:A
__________ his project, the boy had to stay up late.
A.Not finishing
B.Not finished
C.Having not finished
D.Not having finished
蒸汽中断的处理方法。