A.\(\dfrac{{\pi {a^2}}}{{\sqrt 3 }}\)
B.\(\dfrac{{2\pi {a^2}}}{{\sqrt 3 }}\). 
C.\(4\pi {a^2}\).
D.\(2\sqrt 3 \pi {a^2}\).

A.\(\sqrt 3 \).
B.\(3\)
C.\(5\)
D.\(\sqrt 5 \).

A.\(27\).
B.\(5\).
C.\(20\).
D.\(23\).

A.\(2\)
B.\(6\).
C.\(4\).
D.\(3\).

A.A. \((7;1)\).   
B.B.  \((0;7)\).
C.C.  \((5;1)\).
D.D.  \((7;0)\).

A.0
B.1
C.2
D.3

A.A. \({u_5} = \dfrac{{ - 27}}{{16}}.\)   
B.B.  \({u_5} = \dfrac{{ - 16}}{{27}}.\)
C.C.  \({u_5} = \dfrac{{16}}{{27}}.\)
D.D.  \({u_5} = \dfrac{{27}}{{16}}.\)

A.A. \(7\).  
B.B.  \(10\).
C.C.  \(14\).
D. D.  \(6\).

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

A.A.  \(\left( {0;1;0} \right)\).
B.B.  \(\left( {2;1;0} \right)\).
C.C.  \(\left( {0;0; - 1} \right)\).
D.D.  \(\left( {2;0;0} \right)\).