Insert k arithmetic means between 1 and $k^2$ . what is the resulting series?

Question

$(a)\;1,k,k^2\qquad(b)\;1,k,k+1,k+2\;---\;k^2\qquad(c)\;1,k,2k-1,3k-2\;---k^2-k+1,k^2\qquad(d)\;1,k,2k,3k\;--\;k^2$