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.\(10\pi {a^2}.\)

A.\(\dfrac{{1042}}{{225}}.\)
B.\(\dfrac{{208}}{{225}}.\)
C.\(\dfrac{{242}}{{225}}.\)
D.\(\dfrac{{149}}{{225}}.\)

A.\(7.\)
B.\(4.\)
C.\(5.\)
D.\(6.\)

A.Mg(OH)2.
B.MgCl2.
C.MgO.
D.Mg(NO3)2.