Trong không gian Oxyz, cho ba v...

Câu hỏi: Trong không gian Oxyz, cho ba vectơ 

A. $\left(\overrightarrow{\mathrm{a}}.\overrightarrow{\mathrm{b}}\right)\overrightarrow{\mathrm{c}}={\mathrm{x}}_1{\mathrm{x}}_2{\mathrm{x}}_3+{\mathrm{y}}_1{\mathrm{y}}_2{\mathrm{y}}_3+{\mathrm{z}}_1{\mathrm{z}}_2{\mathrm{z}}_3$

B. $\left(\overrightarrow{\mathrm{a}}.\overrightarrow{\mathrm{b}}\right)\overrightarrow{\mathrm{c}}=\overrightarrow{0} \mathrm{khi} \mathrm{và} \mathrm{chỉ} \mathrm{khi} \overrightarrow{\mathrm{a}}\perp \overrightarrow{\mathrm{b}} \mathrm{hoặc} \overrightarrow{\mathrm{c}}=\overrightarrow{0}$

C. $\left(\overrightarrow{\mathrm{a}}.\overrightarrow{\mathrm{b}}\right)\overrightarrow{\mathrm{c}}\ge \overrightarrow{0}$

D. $\left(\overrightarrow{\mathrm{a}}.\overrightarrow{\mathrm{b}}\right)\overrightarrow{\mathrm{c}}=\left(\overrightarrow{\mathrm{c}}.\overrightarrow{\mathrm{b}}\right)\overrightarrow{\mathrm{a}} \mathrm{với} \mathrm{mọi} \overrightarrow{\mathrm{a}},\overrightarrow{\mathrm{b}},\overrightarrow{\mathrm{c}}$