A:a<b<c
B:b<a<c
C:b<c<a
D:c<b<a
某人第一次向南走40km,第二次向北走30km,第三次向北走40km,那么最后相当于这人( )
仙人掌的叶适应沙漠干旱生活逐渐变为刺状.这是( )
It takes me two hours ______ my homework every day.