A.are preventing
B.can prevent
C.prevent
D.can be prevented

A.occasion
B.fortune
C.chance
D.outlook

A.4,02.
B.4,20.
C.4,26.
D.6,03.

A.Polietilen.
B.Poliisopren.
C.Poliacrilonitrin.
D.Poli(vinyl clorua).

A.3
B.4
C.5
D.6

A.Anilin.
B.Alanin.
C.Lysin.
D.Glyxin.

A.Glucozơ.
B.Saccarozơ.
C.Xenlulozơ.
D.Amilozơ.

A.Axit axetic.
B.Axit acrylic.
C.Axit benzoic.
D.Axit stearic.

A.2
B.4
C.6
D.8

A.H2.
B.O2.
C.N2.
D.CO2.