A mass $M$, attached to a horizontal spring, executes S.H.M. with amplitude $A_{1}$. When the mass $M$ passes through its mean position then a smaller mass m is placed over it and both of them move together with amplitude $A_{2}$. The ratio of $\left(\frac{A_{1}}{A_{2}}\right)$ is:\\
(1) $\frac{M+m}{M}$\\
(2) $\left(\frac{M}{M+m}\right)^{1/2}$\\
(3) $\left(\frac{M+m}{M}\right)^{1/2}$\\
(4) $\frac{M}{M+m}$