Suppose That A, B, C, and D Are Four Distinct $\vec{AB}$

Suppose that A, B, C, and D are four distinct points in 3-space.Which of the following must be true? Mark all correct answers.

A) $\vec{AB}$ + $\vec{CD}$ = $\vec{AD}$
B) $$\vec { A B } + \vec { B C } = \vec { A C }$$
C) $$( \overrightarrow { A \bar { B } } + \overrightarrow { C D } ) + \overrightarrow { B C } = \overrightarrow { A D }$$

D) $$( \overrightarrow { BC } + \overrightarrow { C D } ) + \overrightarrow { DA } = \overrightarrow { BA }$$