Cho các vec tơ u1(x1,y1,z1); u2(x2,y2,z2) . Khi đó:

A. $\overrightarrow{u_1}.\overrightarrow{u_2}=\left(x_1{x}_2;y_1{y}_2;z_1{z}_2\right)$

B. $\overrightarrow{u_1}.\overrightarrow{u_2}=x_1{x}_2+y_1{y}_2+z_1{z}_2$

C. $\overrightarrow{u_1}.\overrightarrow{u_2}=x_1{x}_2-y_1{y}_2-z_1{z}_2$

D. $\overrightarrow{u_1}.\overrightarrow{u_2}=x_1{y}_1{z}_1+x_2{y}_2{z}_2$