If in an AP $m$ times $\;m^{th}\;$ term equals $n$ times $\;n^{th}$ term , then $\;(m+n)^{th}$ term will be

Question

$(a)\;1\qquad(b)\;0\qquad(c)\;m+n\qquad(d)\;(m+n)\;a_{m}$