On a day you can see the city from here.
A:warm
B:busy
C:short
D:clear
下列事实不能用分子观点解释的是( )
已知函数f(x)=lnxx(x∈(0,+∞)).
(Ⅰ)求函数f(x)的极值;
(Ⅱ)若对任意的x≥1,都有f(x)≥k(x+3x)+2,求实数k的取值范围.