A:N2和H2在一定条件下生成NH3
B:NO与O2反应生成NO2
C:NH3经催化氧化生成NO
D:由NH3制碳酸氢铵和硫酸铵
He didn't do his best, so I didn't ____ ____ ____ him.
下列不是撒哈拉以南非洲面临的问题是( )