The skin, an ________ part of your body and its largest organ, ________ as a barrier against diseases.
A:vital; acting
B:vital; acts
C:essential; acting
D:essential; acts
选 项
物 质
杂 质
试剂
方法
A
CO2
CO
O2
点燃
B
NaOH溶液
NaCl
适量稀盐酸
蒸发
C
CaO
CaCO3
H20
过滤
D
Cu
Fe
过量稀硫酸