A:石漠化严重
B:水土流失严重
C:土地荒漠化加剧
D:生物多样性锐减
① 2O2(g)+N2(g)=N2O4(l) ΔH1
② N2(g)+2H2(g)=N2H4(l) ΔH2
③ O2(g)+2H2(g)=2H2O(g) ΔH3
④ 2 N2H4(l)+N2O4(l)=3N2(g)+4H2O(g) ΔH4=﹣1048.9 kJ·mol-1
时钟9点30分时,分针和时针之间形成的角的度数等于( )
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