A.\(\dfrac{{a\sqrt {21} }}{7}\)
B.\(\dfrac{{a\sqrt {21} }}{3}\)
C.\(a\sqrt 2 \)
D.\(a\)

A.\(k = \ln 3\)
B.\(k = \ln \dfrac{8}{3}\)
C.\(k = \dfrac{2}{3}\ln 4\)
D.\(k = \ln 2\)

A.\(\dfrac{{3{a^3}}}{4}\)
B.\(\dfrac{{{a^3}}}{2}\)
C.\(\dfrac{{3{a^3}}}{8}\)
D.\(\dfrac{{{a^3}}}{4}\)

A.\(x + 3y + z - 6 = 0\)
B.\(3x - y - z + 6 = 0\)
C.\(x + 3y + z - 5 = 0\)
D.\(3x - y - z - 6 = 0\)

A.\(32\pi \)
B.\(72\pi \)
C.\(24\pi \)
D.\(96\pi \)

A.\({a^3}\)
B.\(\dfrac{{{a^3}}}{2}\)
C.\(\dfrac{{{a^3}}}{6}\)
D.\(\dfrac{{{a^3}}}{3}\)

A.\(\overrightarrow b  = \left( {1;1;0} \right)\)
B.\(\overrightarrow c  = \left( { - 2;2;2} \right)\)
C.\(\overrightarrow d  = \left( { - 1;2;1} \right)\)
D.\(\overrightarrow a  = \left( { - 1;1;0} \right)\)

A.\({x^2} + {\left( {y - 1} \right)^2} + {z^2} = 9.\) 
B.\({\left( {x - 2} \right)^2} + {\left( {y + 1} \right)^2} + {\left( {z + 1} \right)^2} = 9.\)
C.\({\left( {x + 2} \right)^2} + {\left( {y - 1} \right)^2} + {\left( {z - 1} \right)^2} = 9.\)
D.\({x^2} + {\left( {y + 1} \right)^2} + {z^2} = 9.\)

A.\(\dfrac{{x + 5}}{1} = \dfrac{{y - 3}}{{ - 2}} = \dfrac{{z + 2}}{1}\)
B.\(\dfrac{{x - 5}}{1} = \dfrac{{y + 3}}{{ - 2}} = \dfrac{{z - 2}}{{ - 1}}\)
C.\(\dfrac{{x - 6}}{1} = \dfrac{{y + 5}}{{ - 2}} = \dfrac{{z - 3}}{1}\)
D.\(\dfrac{{x + 5}}{1} = \dfrac{{y + 3}}{{ - 2}} = \dfrac{{z - 2}}{1}\)

A.\(21\)
B.\(10\)
C.\(18\)
D.\(20\)