5. In $\triangle A B C$, $\angle B A C: \angle A B C: \angle A C B=4: 2: 1$, $A D$ is the angle bisector of $\angle B A C$. There are the following three conclusions:
(1) $B C: A C: A B=4: 2: 1$;
(2) $A C=A D+A B$;
(3) $\triangle D A C \sim \triangle A B C$.
Among the correct conclusions are ( ).
(A)(1)(2)
(B)(2)(3)
(C)(1)(3)
(D)(1)(2)(3)
5.B.

It is clear that (1) is not correct. As shown in Figure 6, on $AC$, intercept $AE$ such that $AE = AB$. Connect $DE$, then $\triangle ABD \cong \triangle AED$. Therefore,
$$
CE = DE = AD \text{.}
$$

Thus, $AC = AD + AB$. Hence (2) is correct.
Since the ratio of the interior angles of $\triangle DAC$ and $\triangle ABC$ is $4:2:1$, therefore, $\triangle DAC \sim \triangle ABC$. Hence (3) is correct.