一定条件下，下列反应中水蒸气含量随反应时间的变化趋势符合如图的是(    )

A．CO2(g)＋2NH3(g)CO(NH2)2(s)＋H2O(g)ΔH<0

B．CO2(g)＋H2(g)CO(g)＋H2O(g)ΔH>0

C．CH3CH2OH(g)CH2===CH2(g)＋H2O(g)ΔH>0

D．2C6H5CH2CH3(g)＋O2(g)===2C6H5CH===CH2(g)＋2H2O (g)ΔH<0