US 10,303,056 B2  12  11  -continued  -continued  Examples of the monomer Mb2 are given below, but not  limited thereto. Herein  RA  and  RB  are as defined above.  The acid labile groups represented by R 3  and R 4  may be  selected from a variety of such groups. The acid labile  groups may be the same or different and preferably include  groups of the following formulae (A-1) to (A-3).  RA  RA  0  0  ~  0  0  RA  RA  Aro  Aro  0  0  OR 4  OR 4  (A-1)  RA  O  0  o~o  ~  OR 4  R’O};’  R $^{4}$0  OR 4  OR 4  OR 4 