如果想要将一个二维列表matrix = [[1,2],[3,4],[5,6]]扁平化为[1,2,3,4,5,6],应使用下列哪个列表推导式?
[item for item in matrix]
[item for row in matrix for item in row]
[row for row in matrix for item in row]
[row for item in matrix for item in row]