问题: AtpresentinChinatheTBinfectionrate
A: inruralareasisthreetimesashighasthatinurbanareas.
B:inruralareasisnearlyfourtimesashighasthatinurbanareas
C:inurbanareasistwotimeslowerthanthatinruralareas.
D:Inurbanareasisfourtimeslowerthanthatinruralareas.
