为探究水电解的微观过程，王玲同学做了些分子、原子的模型，其中能保持氢气化学性质的粒子模型是[ ]
A．
B．
C．
D．
答案：A
Was it on that morning _____ you left for Beijing _____ he discovered our secret?[ ]
A. that; where
B. which; that
C. when; that
D. that; when
反映任意证券组合的期望收益率和总风险水平之间均衡关系的模型是证券市场线。
