4. In a scalene $\triangle ABC$, $\angle BAC=60^{\circ}$, points $D$ and $E$ are on sides $AB$ and $AC$ respectively, such that $BD=DE=EC$. Then the relationship between $BF$ and $CF$ is ( ).
(A) $BF>CF$
(B) $BF=CF$
(C) $BF<CF$
(D) Uncertain
4. B.

Let $\angle D B E=\angle B E D=\alpha$, $\angle C D E=\angle D C E=\beta$. Then, $\angle A D E=2 \alpha, \angle A E D=2 \beta$.
Thus, $\angle B F D=\alpha+\beta$ $=\frac{1}{2}\left(180^{\circ}-\angle B A C\right)=\angle B A C$
$\Rightarrow A, D, F, E$ are concyclic
$$
\begin{array}{l}
\Rightarrow \angle D A F=\angle D E F=\angle A B E \\
\Rightarrow A F=B F .
\end{array}
$$

Similarly, $A F=C F$.
Therefore, $B F=C F$.