A joint probability of A and B must always be:（）

A. less than or equal to the conditional probability of A given B.

B. greater than or equal to the conditional probability of A given B.

C. greater than or equal to than the probability of A or B.

下列变化过程无法通过“形状补间”实现的是（）

A.一个圆形颜色逐渐变浅直至消失

B.一个圆形沿折线移动

C.一个圆形从舞台左边移动到右边

D.一个红色的圆形逐渐变成绿色的圆形