—______ do you visit your grandparents?
— Every two weeks.
A:How often
B:How far
C:How long
D:How soon
下图是初中化学中有关甲、乙、丙、丁四种常见物质间的转化关系图。下列说法正确的是( )
一辆轿车在平直的高速公路上匀速行驶2.3km,轿车上的速度表如图所示,在此过程中若轿车发动机的功率为40kW,则该车行驶中所受阻力____N,这段过程中轿车消耗汽油0.25kg,其发动机的效率多大____(q汽油=4.6×107J/kg).
__________ these notebooks?