A.\(\left( { - 2;4; - 1} \right).\)                               
B.\(\left( {2; - 4;1} \right).\)       
C.\(\left( {2;4;1} \right).\)         
D.\(\left( { - 2; - 4; - 1} \right)\)

A.\(\overrightarrow {{n_3}}  = \left( {2;3;2} \right).\)  
B.\(\overrightarrow {{n_1}}  = \left( {2;3;0} \right).\)                                
C.\(\overrightarrow {{n_2}}  = \left( {2;3;1} \right).\)      
D.\(\overrightarrow {{n_4}}  = \left( {2;0;3} \right).\)

A.\(P\left( {1;2; - 1} \right).\)       
B.\(M\left( { - 1; - 2;1} \right).\) 
C.\(N\left( {2;3; - 1} \right)\).                            
D.\(Q\left( { - 2; - 3;1} \right).\)

A.\({30^0}.\)                
B.\({45^0}.\)
C.\({60^0}.\)    
D.\({90^0}.\)

A.\(3.\)                   
B.\(0.\)                          
C.\(2.\)               
D.\(1.\)

A.\(2.\)           
B.\( - 23.\)                   
C.\( - 22.\)                    
D.\( - 7.\)

A.\(a + 2b = 2.\)        
B.\(4a + 2b = 1.\)            
C.\(4ab = 1.\)              
D.\(2a + 4b = 1.\)

A.\(3.\)                  
B.\(0\).                         
C.\(2.\)                
D.\(1.\)

A.\(\left[ {0; + \infty ).} \right.\)                       
B.\(\left( {0; + \infty } \right).\) 
C.\(\left( {1; + \infty } \right).\)               
D.\(\left[ {1; + \infty ).} \right.\)

A.\(5\pi {a^2}.\)            
B.\(\sqrt 5 \,\pi {a^2}.\)    
C.\(2\sqrt 5 \pi {a^2}.\)    
D.\(10\pi {a^2}.\)