如图，正六边形 $ABCDEF$ 中，有下列四个命题：

A．	$\stackrel{\rightharpoonup }{AC}+\stackrel{\rightharpoonup }{AF}=2\stackrel{\rightharpoonup }{BC}$
B．	$\stackrel{\rightharpoonup }{AD}=2\stackrel{\rightharpoonup }{AB}+2\stackrel{\rightharpoonup }{AF}$
C．	$\stackrel{\rightharpoonup }{AC}·\stackrel{\rightharpoonup }{AD}=\stackrel{\rightharpoonup }{AD}·\stackrel{\rightharpoonup }{AB}$
D．	$\left(\stackrel{\rightharpoonup }{AD}·\stackrel{\rightharpoonup }{AF}\right)\stackrel{\rightharpoonup }{EF}=\stackrel{\rightharpoonup }{AD}\left(\stackrel{\rightharpoonup }{AF}·\stackrel{\rightharpoonup }{EF}\right)$

其中真命题的代号是