I have a $R$ commutative ring and an exact sequence of $R$-modules
\begin{aligned} 0 \longrightarrow A \longrightarrow & ~~B \longrightarrow D \longrightarrow 0 \\ & \uparrow \uparrow \\ &~D \end{aligned} I would like to know if there is a canonical morphism $D \rightarrow A$. At first, I thought I could do something with coeaqualizer but I did not succeed. Thanks for help.