28. ΔABC\Delta ABCΔABC中,DDD为ACACAC上一点且满足AD‾=13DC‾\overline{AD}=\frac{1}{3}\overline{DC}AD=31DC,若PPP为BDBDBD上一点,且满足AP→=λAB→+μAC→\overrightarrow{AP}=\lambda \overrightarrow{AB}+\mu \overrightarrow{AC}AP=λAB+μAC,λ\lambdaλ,μ\muμ为正实数,则下列结论正确的是((( )))