If D, E and F are the mid-points of the sides BC, CA and AB of triangle ABC respectively, then \(\overline{\mathrm{AD}}+\frac{2}{3} \overline{\mathrm{BE}}+\frac{1}{3} \overline{\mathrm{CF}}\) =
1
\(\frac{1}{2} \overline{\mathrm{AB}}\)
2
\(\frac{1}{2} \overline{\mathrm{AC}}\)
3
\(\frac{1}{2} \overline{\mathrm{BC}}\)
4
\(\frac{2}{3} \overline{\mathrm{AC}}\)