Arithematic Progressions

Which of the following form an AP? Justify your answer.

(i) –1, –1, –1, –1, …

(ii) 0, 2, 0, 2, …

(iii) 1, 1, 2, 2, 3, 3,…

(iv) 11, 22, 33,…

(v) 1/2, 1/3, 1/4…..

(vi)  2, 2², 2³, 2⁴, …