if f(x) = sin ( 2pi[pi2-x] )/5+[x]2 , [.] denotes greatest integral function ), then f(x) is
(a) discontinuous at some x (b) continuous at all x , but the derivative f'(x) does not exisrs for some x
(c) f'(x) exists for all x , but f'"(x) does not exists (d) f"(x) exists for all x
