弱光下,以为主要氮源的植物表现出缺氮症状。( )
第4题
The relationship between words and things in the world is established by means of
A.reference.
B.sense.
C.concept.
D.meaning.
第5题
第6题
Protecting the earth is a worldwide question because ______
A.pollution is everywhere in the world
B.polluted air and water in one place affects distant areas
C.people all over the world are responsible for the pollution problem
D.all of the above
第8题
A.Y
B.N
C.NG
第9题
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