已知变量a、b已被赋值，要交换a、b的值，采用的算法是（   ）

A．a =" b," b =" a"	B．a =" c," b =" a," c =" b"
C．a =" c," b =" a," c =" a"	D．c =" a," a =" b," b = c

科目 数学   题型 选择题   难度 较易