Which ONE of the following statements is FALSE? OA. If the function f (x,y) is maximum at the point (a,b) then (a,b) is a critical point. B. 0²f If f (x,y) has a minimum at point (a,b) then evaluated at (a,b) is positive. 0x² Oc. If f(x,y) has a saddle point at (a,b) the f(x,y) f(a,b) on some points (x,y) in a domain near point (a,b). D.If (a,b) is one of the critical of f(x,y). then f is not defined on (a,b)