A.\(6a\)
B.\(2a\)
C.\(a\sqrt 3 \)
D.\(3a\)

A.\(\sqrt 8 \)
B.\(\sqrt {34} \)
C.\(34\)
D.\(8\)

A.\(0\)
B.\(2\)
C.\(4\)
D.\(3\)

A.\(\left( {3;7;23} \right)\)
B.\(\left( {7;3;23} \right)\)
C.\(\left( {23;7;3} \right)\)
D.\(\left( {7;23;3} \right)\)

A.\(\dfrac{{\sqrt 3 }}{5}\)
B.\(\dfrac{{2\sqrt 5 }}{5}\)
C.\(\dfrac{{2\sqrt 3 }}{5}\)
D.\(\dfrac{{\sqrt 5 }}{5}\)

A.\(9\)
B.\(1\)
C.\(20\)
D.\(6\)

A.\(2\)
B.\(3\)
C.\(4\)
D.\(5\)

A.\(3x - 2y - z - 7 = 0\)
B.\(x - y + 2z = 0\)
C.\(2x + z = 0\)
D.\(x - 2y + 2z + 2 = 0\)

A.\(\left\{ \begin{array}{l}x =  - 2 + 3t\\y = 1\\z = 1 + 2t\end{array} \right.\)
B.\(\left\{ \begin{array}{l}x = 4 - 3t\\y = 2 + t\\z = 5 + 2t\end{array} \right.\)
C.\(\left\{ \begin{array}{l}x =  - 2 + 3t\\y = t\\z = 1 + 2t\end{array} \right.\)
D.\(\left\{ \begin{array}{l}x =  - 1 + 4t\\y = 2t\\z = 1 + 5t\end{array} \right.\)

A.\(10\)
B.\( - 3\)
C.\(13\)
D.\(3\)