The correct answer is :
$\begin {array} {1 1} (1)\;G_1 \rightarrow G_2 \rightarrow S \rightarrow M & \quad (2)\;S \rightarrow M \rightarrow G_2 \rightarrow G_1 \\ (3)\;G_1 \rightarrow S \rightarrow G_2 \rightarrow M & \quad (4)\;M \rightarrow S \rightarrow G_2 \rightarrow G_1 \end {array}$