L is the set of all bit strings with even number of 1's.
a) (0*10*1)* - It can not accept string 0110 ( I mean a string ends with 0 even if it contains even number of 1's ).
c) 0*(10*1*)*0* - It can accept a string with odd number of 1's. For ex- 01011.
d) 0*1(10*1)*10* - It can not accept any string with zero number of 1's. For ex- 0, 00, 000 etc.
Ans- b) 0*(10*10*)*