水体的物理性污染是指水温、______等污染，给人的感官带来不悦。

A．色度

B．臭味

C．泡沫

D．悬浮物

What is the contrapositive of the relation represented in the exhibit shown below ( )

A．R={＜1,2＞,＜1,3＞,＜1,4＞,＜1,5＞}

B．R={＜1,1＞,＜2,2＞,＜3,3＞,＜4,4＞,＜5,5＞}

C．R={＜2,1＞,＜4,1＞,＜2,2＞,＜1,3＞,＜3,2＞,＜1,4＞,＜4,4＞,＜5,4＞}

D．R={＜1,2＞,＜3,1＞,＜1,4＞,＜2,2＞,＜2,3＞,＜4,1＞,＜4,4＞,＜4,5＞}