What are the difference numbers of these arithmetic sequences?

a) [[$ 1, 2, 3, 4, 5, … $]]

Answer: The difference number of the arithmetic sequence is [[$ d = $]] .

b) [[$ 0, 5, 10, 15, 20, … $]]

Answer: The difference number of the arithmetic sequence is [[$ d = $]] .

c) [[$ -1, -3, -5, -7, -9, … $]]

Answer: The difference number of the arithmetic sequence is [[$ d = $]] .