A.
People used to do house cleaning on the 20 th day of the 12 th month.
B.
People used to do house cleaning on the 21 st day of the 12 th month.
C.
People used to do house cleaning on the 20 th day of the 11 th month.
D.
People used to do house cleaning on the 21 st day of the 11 th month.