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下列哪个语句在python中是非法的，假设事先定义了x=0,y=0,z=0？
A. x = y = z = 1
B. x = (y = z + 1)
C. x, y = y, x
D. x += y
Which of the following statement is illegal in python, assume that x=0, y=0 , z=0first?
A. x = y = z = 1
B. x = (y = z + 1)
C. x, y = y, x
D. x += y