– ________ do you exercise?– I used to exercise every day, but now I exercise twice a week.
A:How often
B:How soon
C:How long
若{an}为等差数列,Sn是其前n项的和,且S11=223π,则tana6=( )
如图,是某日太阳光照图,图示地球自转的方向是( )