健康人、流感、流感病人、流感病人的飞沫、流感病毒分别属于( )
①传染源 ②病原体 ③传播途径 ④传染病 ⑤易感人群.
A:⑤④③①②
B:⑤②③④①
C:①⑤④③②
D:⑤④①③②
x(元/件)
38
36
34
32
30
28
26
t(件)
4
8
12
16
20
24
假定试销中每天的销售量t(件)与销售价x(元/件)之间满足一次函数.
British people say "please" and "thank you" all ______ time, and they always keep their voice down in ______ public.
图中甲乙两地,每逢圣诞节两地日出时刻同步,结合所学知识完成下列各题。
在函数y=x-4中,自变量x的取值范围是____