-- You come to school early every day. __________ is it from your home to school?
-- It's only about one kilometer.
A:How long
B:How much
C:How many
D:How far
已知函数fx=1-3xx+10xx≤6ax-7x>6若数列{an}满足an=fn(n∈N+)且{an}是递减数列,则实数a的取值范围是( )
如表为某人平静呼吸时,吸入气(吸入的气体),呼出气(呼出的气体),肺泡气(肺泡内的气体)中O2、CO2、N2三种成分的体积分数,下列说法正确的是( )
O2
CO2
N2
吸入气
23%
0.04%
78%
呼出气
16%
4.0%
肺泡气
14%
5.6%
随着国民经济的发展,汽车已走进家庭.一辆小轿车以某一速度在平直路面上匀速行驶100km,消耗汽油10L.若这些汽油完全燃烧放出的热量有30%用来驱动汽车做有用功,所用汽油的热值为4.6×107J/kg,密度为0.7×103kg/m3,求: