A.
Mxy由小变大的过程 The process of Mxy increasing to the maximum
B.
Mxy由大变为零过程 The process of Mxy decreasing from the maximum to zero
C.
Mz由大变小的过程 The process of Mz decreasing from the maximum to zero
D.
Mz由小变大的过程 The process of Mz increasing to the maximum