看谱分析中,所谓谱线强度是指谱线的黑度。
参考答案:错
One reason why_____plane is such a popular means of_____transport is that it is very fast and safe.
A.the; /
B.a; the
C.a;/
D.the; the
简述我国当前卫生防疫机构的类型。