What is the contrapositive of the relation
题型：单项选择题
问题：
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＞}