Supervisor mode is entered when the processor encounters a software interrupt instruction. Thus, A matches with I. Abort mode is entered in response to a memory fault. Thus, B matches with II. Fast interrupt mode is entered whenever the processor receives an interrupt signal from the designated fast interrupt source. Thus, C matches with III. Interrupt mode is entered whenever the processor receives an interrupt signal from any other interrupted source. Thus, D matches with IV. Therefore, the correct answer is: (4) (A) - (I), (B) - (II), (C) - (III), (D) - (IV).