15. The function $f ( x ) = [ x ] 2 - [ x 2 ]$ (where [y] is the greatest integer less than or equal to $y$ ), is discontinuous at : (A) all integers (B) all integers except 0 and 1 (C) all integers except 0 (D) all integers except 1
15. The function $f ( x ) = [ x ] 2 - [ x 2 ]$ (where [y] is the greatest integer less than or equal to $y$ ), is discontinuous at :\\
(A) all integers\\
(B) all integers except 0 and 1\\
(C) all integers except 0\\
(D) all integers except 1\\