= Solution
\b[The dominant interaction is strong.] At <hadron> level, panel (iii) is an <effective hadronic vertex> for $\Delta p\pi$. The initial $uuu$ constituents rearrange into $uud$ and $u\bar d$ after creation of a $d\bar d$ pair:
$$
uuu\longrightarrow (uud)+(u\bar d).
$$
One original <up quark> enters the charged <pion>; the other two join the new <down quark> in the <proton>. Gluon-induced pair creation supplies the <quark-flow diagram> interpretation. This is nonperturbative <hadronization>: the <effective hadronic vertex> does not claim that one elementary perturbative <quark> graph calculates its width. Charge, <baryon number> and net <quark> flavor are conserved.
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