下列说法正确的是[ ]
A.CO具有可燃性故用于冶炼金属
B.塑料属于天然有机高分子材料
C.洁净的空气属于纯净物
D.N2化学性质稳定,故食品包装时充氮以防腐
答案:D
He told me his computer company was in great need of a capable leader, ________ with strong will as well as good humor.[ ]
A.who
B.that
C.one
D.which
胎盘的组成包括()
A.羊膜、包蜕膜、底蜕膜
B.羊膜、底蜕膜、真蜕膜
C.羊膜、叶状绒毛膜、真蜕膜
D.羊膜、叶状绒毛膜、底蜕膜
E.包蜕膜、底蜕膜、真蜕膜