If a charged particle is projected perpendicular to a uniform magnetic field, then `a)` it revolves in circular path
`b)` its `K.E.` remains constant
`c)` its momentum remains constant
`d)` its path is psiral
A. only`a,b` are correct
B. only `a,c,` are correct
C. only`b,d` are correct
D. only `a,d` are correct
