Option A, current (thumb) to magnetic field (fingers)
As per the First right-hand rule, 
Using right hand, if we suppose that thumb points towards the electric current
fingers curl towards the magnetic field
 
        
                    
             
        
        
        
The answer for this question is Control Variable because it doesn’t change throughout the experiment.
        
             
        
        
        
Answer:
m = 14*26 = 364
Explanation:
overall magnification is given as m 

mo magnification of objective lens
me magnification of EYE lens
where mo is given as
 
and me as

d is distant of distinct vision = 25.0 cm for normal eye
fe =  focal length of eye piece
focal length of objective lense is 0.140 cm
we know that








m = 14*26 = 364
 
        
             
        
        
        
B precipitation,condensation,precipitation
        
             
        
        
        
Answer:
magnification is - 159 
objective distance is 3.85 cm
Explanation:
Given data 
focal length f1 = 1.40 cm 
focal length f2 = 2.20 cm
separated d = 19.6 cm
to find out
angular magnification and How far from the objective 
solution
we know magnification formula that is
magnification = ( - L / f1 ) (D/f2)
here D = 25 cm put all value 
magnification = ( - 19.6 / 1.40 ) (25/2.20)
magnification = - 159 
and
now we apply lens formula
i/f = 1/q + 1/p
p = f2 = 2.20 
so 
q = f2 p / p -f2 
q = 1.4(2.20) / ( 2.2 - 1.4 )
q = 3.85 cm
so objective distance is 3.85 cm