- Could you tell me_______？

- Every four years.

A．how often the Olympic Games take place

B．when the Olympic Games are held

C．how often are the Olympic Games held

D．how often the Olympic Games were held

铜有两种常见的氧化物CuO和Cu₂O。某学习小组取0.98  g(用精密天平测量)Cu(OH)₂固体，将其加热有铜的氧化物生成，其质量随温度变化的曲线如图1所示。

另外，某同学绘制了三条表示金属氧化物与其所含金属元素质量的关系曲线，如图2所示。则下列分析正确的是

A．图1中产物A、B的化学式分别为Cu₂O和CuO

B．图1整个过程中共生成0.26  g  H₂O

C．图2三条曲线中，表示CuO和其中所含Cu元素质量的关系曲线是曲线A

D．图2中绘制错误的曲线共2条