For irreversible expansion of an ideal gas under isothermal condition, the correct option is:
(A) \( \Delta U =0, \Delta S _{\text {total }}=0 \)
(B) \( \Delta U \neq 0, \Delta S _{\text {total }} \neq 0 \)
(C) \( \Delta U =0, \Delta S _{\text {total }} \neq 0 \)
(D) \( \Delta U \neq 0, \Delta S _{\text {total }}=0 \)