Let $z _ { 1 }$、$z _ { 2 }$、$z _ { 3 }$、$z _ { 4 }$ be four distinct complex numbers whose corresponding points on the complex plane can be connected in order to form a parallelogram. Which of the following options must be real numbers? (1) $\left( z _ { 1 } - z _ { 3 } \right) \left( z _ { 2 } - z _ { 4 } \right)$ (2) $z _ { 1 } - z _ { 2 } + z _ { 3 } - z _ { 4 }$ (3) $z _ { 1 } + z _ { 2 } + z _ { 3 } + z _ { 4 }$ (4) $\frac { z _ { 1 } - z _ { 2 } } { z _ { 3 } - z _ { 4 } }$ (5) $\left( \frac { z _ { 2 } - z _ { 4 } } { z _ { 1 } - z _ { 3 } } \right) ^ { 2 }$
Let $z _ { 1 }$、$z _ { 2 }$、$z _ { 3 }$、$z _ { 4 }$ be four distinct complex numbers whose corresponding points on the complex plane can be connected in order to form a parallelogram. Which of the following options must be real numbers?\\
(1) $\left( z _ { 1 } - z _ { 3 } \right) \left( z _ { 2 } - z _ { 4 } \right)$\\
(2) $z _ { 1 } - z _ { 2 } + z _ { 3 } - z _ { 4 }$\\
(3) $z _ { 1 } + z _ { 2 } + z _ { 3 } + z _ { 4 }$\\
(4) $\frac { z _ { 1 } - z _ { 2 } } { z _ { 3 } - z _ { 4 } }$\\
(5) $\left( \frac { z _ { 2 } - z _ { 4 } } { z _ { 1 } - z _ { 3 } } \right) ^ { 2 }$