Insert the correct argument to specify that the array should be of type STRING.
arr = np.array([1, 2, 3, 4], @(9))
arr = np.array([1, 2, 3, 4], dtype='S')
arr = np.array([1, 2, 3, 4], dtype="S")
arr = np.array([1, 2, 3, 4], dtype = "S")
arr = np.array([1, 2, 3, 4], dtype = 'S')