很可能引起中毒的氟摄入阈值为每公斤体重（）
A.1mg
B.3mg
C.5mg
D.10mg
E.15mg
参考答案：C
--Where did you see him for the first time?
-- It was in the factory _________ we worked.
A．that
B．where
C．which
D．when
大肠的下合穴是
A．上巨虚B．足三里C．下巨虚D．委阳
