= Solution
The <Erdős-Stone theorem> states precisely that, for every fixed graph $H$ with <chromatic number> $\chi(H)\geq2$,
$$
\lim_{n\to\infty}
\frac{\operatorname{ex}(n,H)}{\binom n2}
=1-\frac1{\chi(H)-1}.
$$
If the bipartite graph $G$ has an edge, then $\chi(G)=2$. Substitution into the theorem gives
$$
\boxed{
\frac{\operatorname{ex}(n,G)}{\binom n2}\longrightarrow
1-\frac1{2-1}=0.}
$$
If $G$ has no edges, then every graph of sufficiently large order contains $G$ as a <subgraph>, so the conclusion is immediate.
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