If `f:RR⃗ rarr RR` is a function defined by `f(x)=[x]cos((2x−1)/2)pi` where `[x]` denotes the greatest integer function, then `f` is (1) continuous for every real x (2) discontinuous only at `x=0` (3) discontinuous only at non-zero integral values of x (4) continuous only at `x=0`.