A:beyond
B:over
C:off
D:above
There are two____(千)students in the school.
Are they going to____ (clean) their classroom?
微量元素在生物体内含量虽然很少,却是维持正常生命活动不可缺少的.这可通过下面的哪一实例得到证实( )
人体内有“生命中枢”之称的结构是( )