What is difference between both and please share answer also

Let f: R2 R R be lefined by f(x.y)=* +y?, if x and y are irrationals 14. 0, otherwise Then (A) f is not continuous at (0, 0) (B) fis continuous at (0, 0) but not differentiable at (0, 0) (C) f is differentiable only at (0, 0) (D) fis differentiable everywhere 15. Let f: R2 R be defined by x+y2, if x and y rational 0 f(x,y)= otherwise Then (A) f is not continuous at (0, 0) (B) fis continuous at (0, 0) but not differentiable at (0, 0) (C) fis differentiable only at (0, 0) fis differentiable everywhere (D)