Given a+b+c+d=0 , which of the following statements are correct
(a) a,b,c and d must each be null vector ,
(b) The magnitude of (a+c) equals the magnitude of (b+d),
(c ) The magnitude of a can never be greater than the sum of the magnitudes of b ,c and d,
(d) b+c must lie in the plane of and d if a and d are not collinear , and in the line of a and d , if they are collimear ?

Answer

All statements except (a) - are correct